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Update dependency urllib3 to v2 [SECURITY] - #5497

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Update dependency urllib3 to v2 [SECURITY]#5497
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renovate/pypi-urllib3-vulnerability

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This PR body was truncated due to platform limits.

This PR contains the following updates:

Package Change Age Confidence
urllib3 (changelog) ==1.26.5 → ==2.8.0 age confidence

Cookie HTTP header isn't stripped on cross-origin redirects

CVE-2023-43804 / GHSA-v845-jxx5-vc9f

More information

Details

urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.

Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the Cookie header, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

  • Using an affected version of urllib3 (patched in v1.26.17 and v2.0.6)
  • Using the Cookie header on requests, which is mostly typical for impersonating a browser.
  • Not disabling HTTP redirects
  • Either not using HTTPS or for the origin server to redirect to a malicious origin.
Remediation
  • Upgrading to at least urllib3 v1.26.17 or v2.0.6
  • Disabling HTTP redirects using redirects=False when sending requests.
  • Not using the Cookie header.

Severity

  • CVSS Score: 7.4 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3's request body not stripped after redirect from 303 status changes request method to GET

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4

More information

Details

urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 303 "See Other" after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although the behavior of removing the request body is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers.

From RFC 9110 Section 9.3.1:

A client SHOULD NOT generate content in a GET request unless it is made directly to an origin server that has previously indicated, in or out of band, that such a request has a purpose and will be adequately supported.

Affected usages

Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable.

Both of the following conditions must be true to be affected by this vulnerability:

  • If you're using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON)
  • The origin service is compromised and starts redirecting using 303 to a malicious peer or the redirected-to service becomes compromised.
Remediation

You can remediate this vulnerability with any of the following steps:

  • Upgrade to a patched version of urllib3 (v1.26.18 or v2.0.7)
  • Disable redirects for services that you aren't expecting to respond with redirects with redirects=False.
  • Disable automatic redirects with redirects=False and handle 303 redirects manually by stripping the HTTP request body.

Severity

  • CVSS Score: 5.7 / 10 (Medium)
  • Vector String: CVSS:4.0/AV:A/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

CVE-2024-37891 / GHSA-34jh-p97f-mpxf

More information

Details

When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.

However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.

Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.

Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

  • Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
  • Not disabling HTTP redirects.
  • Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.
Remediation
  • Using the Proxy-Authorization header with urllib3's ProxyManager.
  • Disabling HTTP redirects using redirects=False when sending requests.
  • Not using the Proxy-Authorization header.

Severity

  • CVSS Score: 4.4 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3 redirects are not disabled when retries are disabled on PoolManager instantiation

CVE-2025-50181 / GHSA-pq67-6m6q-mj2v

More information

Details

urllib3 handles redirects and retries using the same mechanism, which is controlled by the Retry object. The most common way to disable redirects is at the request level, as follows:

resp = urllib3.request("GET", "https://httpbin.org/redirect/1", redirect=False)
print(resp.status)

##### 302

However, it is also possible to disable redirects, for all requests, by instantiating a PoolManager and specifying retries in a way that disable redirects:

import urllib3

http = urllib3.PoolManager(retries=0)  # should raise MaxRetryError on redirect
http = urllib3.PoolManager(retries=urllib3.Retry(redirect=0))  # equivalent to the above
http = urllib3.PoolManager(retries=False)  # should return the first response

resp = http.request("GET", "https://httpbin.org/redirect/1")

However, the retries parameter is currently ignored, which means all the above examples don't disable redirects.

Affected usages

Passing retries on PoolManager instantiation to disable redirects or restrict their number.

By default, requests and botocore users are not affected.

Impact

Redirects are often used to exploit SSRF vulnerabilities. An application attempting to mitigate SSRF or open redirect vulnerabilities by disabling redirects at the PoolManager level will remain vulnerable.

Remediation

You can remediate this vulnerability with the following steps:

  • Upgrade to a patched version of urllib3. If your organization would benefit from the continued support of urllib3 1.x, please contact sethmichaellarson@gmail.com to discuss sponsorship or contribution opportunities.
  • Disable redirects at the request() level instead of the PoolManager() level.

Severity

  • CVSS Score: 5.3 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3 allows an unbounded number of links in the decompression chain

CVE-2025-66418 / GHSA-gm62-xv2j-4w53

More information

Details

Impact

urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, zstd).

However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier for HTTP requests to untrusted sources unless they disable content decoding explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library limits the number of links to 5.

If upgrading is not immediately possible, use preload_content=False and ensure that resp.headers["content-encoding"] contains a safe number of encodings before reading the response content.

Severity

  • CVSS Score: 8.9 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3 streaming API improperly handles highly compressed data

CVE-2025-66471 / GHSA-2xpw-w6gg-jr37

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation.

The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side, even if the application only requested a small chunk of data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier to stream large compressed responses or content from untrusted sources.

stream(), read(amt=256), read1(amt=256), read_chunked(amt=256), readinto(b) are examples of urllib3.HTTPResponse method calls using the affected logic unless decoding is disabled explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library avoids decompressing data that exceeds the requested amount.

If your environment contains a package facilitating the Brotli encoding, upgrade to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 too. These versions are enforced by the urllib3[brotli] extra in the patched versions of urllib3.

Credits

The issue was reported by @​Cycloctane.
Supplemental information was provided by @​stamparm during a security audit performed by 7ASecurity and facilitated by OSTIF.

Severity

  • CVSS Score: 8.9 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Decompression-bomb safeguards bypassed when following HTTP redirects (streaming API)

CVE-2026-21441 / GHSA-38jv-5279-wg99

More information

Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption.

However, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client (high CPU usage and large memory allocations for decompressed data; CWE-409).

Affected usages

Applications and libraries using urllib3 version 2.6.2 and earlier to stream content from untrusted sources by setting preload_content=False when they do not disable redirects.

Remediation

Upgrade to at least urllib3 v2.6.3 in which the library does not decode content of redirect responses when preload_content=False.

If upgrading is not immediately possible, disable redirects by setting redirect=False for requests to untrusted source.

Severity

  • CVSS Score: 8.9 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3: Sensitive headers forwarded across origins in proxied low-level redirects

CVE-2026-44431 / GHSA-qccp-gfcp-xxvc

More information

Details

Impact

When following cross-origin redirects for requests made using urllib3’s high-level APIs, such as urllib3.request(), PoolManager.request(), and ProxyManager.request(), sensitive headers — Authorization, Cookie, and Proxy-Authorization (defined in Retry.DEFAULT_REMOVE_HEADERS_ON_REDIRECT) — are stripped by default, as expected.

However, cross-origin redirects followed from the low-level API via ProxyManager.connection_from_url().urlopen(..., assert_same_host=False) still forward these sensitive headers.

Affected usage

Applications and libraries using urllib3 versions earlier than 2.7.0 may be affected if they allow cross-origin redirects while making requests through HTTPConnection.urlopen() instances created via ProxyManager.connection_from_url().

Remediation

Upgrade to urllib3 version 2.7.0 or later, in which sensitive headers are stripped from redirects followed by HTTPConnection.

If upgrading is not immediately possible, avoid using this low-level redirect flow for cross-origin redirects. If appropriate for your use case, switch to ProxyManager.request().

Severity

  • CVSS Score: 8.2 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3: HTTPS proxy TLS configuration may be ignored or overridden

CVE-2026-97687 / GHSA-8988-9cw3-xx77

More information

Details

Impact

urllib3 supports configuring TLS independently for an HTTPS proxy and the target server.

proxy_ssl_context, proxy_assert_hostname, and proxy_assert_fingerprint configure the TLS connection to the proxy. ssl_context and the other target-specific TLS parameters configure the connection to the target server.

In urllib3 versions 1.26.0 through 2.7.0, these configurations were not consistently separated. Depending on the proxy mode, urllib3 could:

  1. Ignore proxy_ssl_context and use the target server's SSL context for the TLS connection to an HTTPS forwarding proxy.
  2. Override the HTTPS proxy's certificate-verification policy with the target server's certificate-verification policy.
  3. Apply target-specific SNI, hostname assertions, certificate fingerprint assertions, or TLS client credentials to the TLS connection to an HTTPS forwarding proxy.

In particular, configuring cert_reqs="CERT_NONE" for a target server could overwrite the verify_mode of the SSL context configured for the HTTPS proxy. This modification occurred in place and persisted on the context object, potentially disabling proxy certificate verification for later connections that reused the same context.

An attacker able to intercept the connection to an HTTPS proxy may be able to impersonate the proxy when the effective proxy TLS configuration disables certificate verification or otherwise accepts the attacker's certificate. This may occur, for example, when the target server's trust or identity policy is incorrectly applied to the proxy connection.

When HTTPS forwarding is enabled, an impersonated proxy can observe or modify forwarded requests and responses, potentially exposing credentials, authentication tokens, request bodies, response data, and other sensitive information.

A TLS client certificate intended for the target server may also be presented to the proxy or to an attacker impersonating it. This can disclose the client's identity and provide proof of possession of the corresponding private key. The private key itself is not transmitted during the TLS handshake.

In CONNECT tunneling mode, impersonating the HTTPS proxy does not by itself defeat the separate end-to-end TLS connection between the client and the target server.

Affected Usages

Code using urllib3 versions 1.26.0 through 2.7.0 may be affected in any of the following cases.

1. The target SSL context is used for an HTTPS forwarding proxy

HTTPS requests are forwarded through an HTTPS proxy with use_forwarding_for_https=True, and proxy_ssl_context is configured for the proxy.

urllib3 may ignore proxy_ssl_context and use the target server's ssl_context for the proxy TLS handshake. The proxy may therefore be verified using the target server's trust and certificate policy instead of the policy explicitly configured for the proxy.

2. The target verification policy overrides the proxy policy

An HTTPS proxy is configured with proxy_ssl_context, while the target server uses a different certificate-verification policy.

urllib3 may apply the target server's cert_reqs value to the proxy SSL context. For example, setting cert_reqs="CERT_NONE" for the target server may also disable certificate verification for the HTTPS proxy, even when proxy_ssl_context was configured to require verification.

This issue can affect the TLS connection to an HTTPS proxy in both forwarding and CONNECT tunneling configurations.

3. A mutated proxy SSL context is reused

The same SSL context is reused as proxy_ssl_context across multiple connections, and certificate verification is disabled for one target server.

urllib3 may modify the proxy SSL context's verify_mode in place. Later connections that reuse the same context may therefore connect to the HTTPS proxy without certificate verification.

4. Target-specific TLS identity or credentials are applied to the proxy

HTTPS requests are forwarded through an HTTPS proxy with use_forwarding_for_https=True, and target-specific SNI, hostname assertions, certificate fingerprint assertions, or TLS client credentials are configured.

urllib3 may apply these target-specific settings to the proxy TLS handshake. This may cause urllib3 to:

  • send SNI intended for the target server to the proxy;
  • verify the proxy using a hostname or certificate fingerprint intended for the target server; or
  • present a TLS client certificate intended for the target server to the proxy.

Code connecting through a plain HTTP proxy does not establish a TLS connection to the proxy and is not affected by this issue.

Remediation

Upgrade to urllib3 2.8.0 or later.

urllib3 2.8.0 independently applies the explicitly configured proxy_ssl_context and proxy-specific certificate assertions to the HTTPS proxy connection. Target-specific SNI, certificate assertions, and TLS client certificate parameters are no longer applied to the HTTPS proxy handshake.

For backward compatibility, when an HTTPS proxy is used with use_forwarding_for_https=True and proxy_ssl_context is not provided, urllib3 2.8.0 continues to use ssl_context for the TLS connection to the proxy. This configuration emits a FutureWarning. In urllib3 3.0, passing ssl_context with use_forwarding_for_https=True for an HTTPS proxy will raise an error. Applications should use proxy_ssl_context to configure TLS for an HTTPS forwarding proxy.

The fixes were implemented in commits b6447295fff7b38fdffc67e0df9712d60cef3cc3 and 07408cec79d1856d81bb42c74a904a24fdb9e465.

Severity

  • CVSS Score: 7.6 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory

CVE-2026-97689 / GHSA-vxq7-64xx-v4gw

More information

Details

Impact

urllib3's streaming API is designed for efficiently handling large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. When decoding a chunked-transfer-encoded response, this API reads each chunk's size field by buffering until it sees \n or EOF.

A malicious HTTP server can return Transfer-Encoding: chunked and then send a very long run of bytes without any newline, causing the streaming client to buffer that entire run before urllib3 can reject the chunk size as invalid and allocate more memory than intended.

To fix the issue, we'll reject chunk-size fields larger than 65536 bytes, as already done in the non-streaming case, which is currently handled by the Python standard library. Note that this only applies to reading the chunk-size field, not the chunk data, which is already handled correctly. Thus, there shouldn't be any impact for non-malicious servers.

Affected usages

Applications and libraries using urllib3 versions earlier than 2.8.0 may be affected when streaming a chunked response from untrusted sources. Specifically, this affects the read_chunked() and stream() methods of the HTTPResponse object.

This also affects requests streaming API, which uses urllib3 under the hood.

Remediation

Upgrade to urllib3 version 2.8.0 or later, where chunk-size fields larger than 65536 will be rejected. If upgrading is not immediately possible, consider reading the response at once using the read() method.

Severity

  • CVSS Score: 8.9 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

References

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

Cookie HTTP header isn't stripped on cross-origin redirects

CVE-2023-43804 / GHSA-v845-jxx5-vc9f / PYSEC-2023-192

More information

Details

urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly.

Users must handle redirects themselves instead of relying on urllib3's automatic redirects to achieve safe processing of the Cookie header, thus we decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

  • Using an affected version of urllib3 (patched in v1.26.17 and v2.0.6)
  • Using the Cookie header on requests, which is mostly typical for impersonating a browser.
  • Not disabling HTTP redirects
  • Either not using HTTPS or for the origin server to redirect to a malicious origin.
Remediation
  • Upgrading to at least urllib3 v1.26.17 or v2.0.6
  • Disabling HTTP redirects using redirects=False when sending requests.
  • Not using the Cookie header.

Severity

  • CVSS Score: 7.4 / 10 (High)
  • Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2023-43804 / GHSA-v845-jxx5-vc9f / PYSEC-2023-192

More information

Details

urllib3 is a user-friendly HTTP client library for Python. urllib3 doesn't treat the Cookie HTTP header special or provide any helpers for managing cookies over HTTP, that is the responsibility of the user. However, it is possible for a user to specify a Cookie header and unknowingly leak information via HTTP redirects to a different origin if that user doesn't disable redirects explicitly. This issue has been patched in urllib3 version 1.26.17 or 2.0.5.

Severity

  • CVSS Score: 8.1 / 10 (High)
  • Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3's request body not stripped after redirect from 303 status changes request method to GET

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4 / PYSEC-2023-212

More information

Details

urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 303 "See Other" after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although the behavior of removing the request body is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers.

From RFC 9110 Section 9.3.1:

A client SHOULD NOT generate content in a GET request unless it is made directly to an origin server that has previously indicated, in or out of band, that such a request has a purpose and will be adequately supported.

Affected usages

Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable.

Both of the following conditions must be true to be affected by this vulnerability:

  • If you're using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON)
  • The origin service is compromised and starts redirecting using 303 to a malicious peer or the redirected-to service becomes compromised.
Remediation

You can remediate this vulnerability with any of the following steps:

  • Upgrade to a patched version of urllib3 (v1.26.18 or v2.0.7)
  • Disable redirects for services that you aren't expecting to respond with redirects with redirects=False.
  • Disable automatic redirects with redirects=False and handle 303 redirects manually by stripping the HTTP request body.

Severity

  • CVSS Score: 5.7 / 10 (Medium)
  • Vector String: CVSS:4.0/AV:A/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

CVE-2023-45803 / GHSA-g4mx-q9vg-27p4 / PYSEC-2023-212

More information

Details

urllib3 is a user-friendly HTTP client library for Python. urllib3 previously wouldn't remove the HTTP request body when an HTTP redirect response using status 301, 302, or 303 after the request had its method changed from one that could accept a request body (like POST) to GET as is required by HTTP RFCs. Although this behavior is not specified in the section for redirects, it can be inferred by piecing together information from different sections and we have observed the behavior in other major HTTP client implementations like curl and web browsers. Because the vulnerability requires a previously trusted service to become compromised in order to have an impact on confidentiality we believe the exploitability of this vulnerability is low. Additionally, many users aren't putting sensitive data in HTTP request bodies, if this is the case then this vulnerability isn't exploitable. Both of the following conditions must be true to be affected by this vulnerability: 1. Using urllib3 and submitting sensitive information in the HTTP request body (such as form data or JSON) and 2. The origin service is compromised and starts redirecting using 301, 302, or 303 to a malicious peer or the redirected-to service becomes compromised. This issue has been addressed in versions 1.26.18 and 2.0.7 and users are advised to update to resolve this issue. Users unable to update should disable redirects for services that aren't expecting to respond with redirects with redirects=False and disable automatic redirects with redirects=False and handle 301, 302, and 303 redirects manually by stripping the HTTP request body.

Severity

  • CVSS Score: 4.2 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:A/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the PyPI Advisory Database (CC-BY 4.0).

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

CVE-2024-37891 / GHSA-34jh-p97f-mpxf / PYSEC-2026-1995

More information

Details

When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.

However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.

Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.

Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

  • Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
  • Not disabling HTTP redirects.
  • Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.
Remediation
  • Using the Proxy-Authorization header with urllib3's ProxyManager.
  • Disabling HTTP redirects using redirects=False when sending requests.
  • Not using the Proxy-Authorization header.

Severity

  • CVSS Score: 4.4 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

urllib3's Proxy-Authorization request header isn't stripped during cross-origin redirects

CVE-2024-37891 / GHSA-34jh-p97f-mpxf / PYSEC-2026-1995

More information

Details

When using urllib3's proxy support with ProxyManager, the Proxy-Authorization header is only sent to the configured proxy, as expected.

However, when sending HTTP requests without using urllib3's proxy support, it's possible to accidentally configure the Proxy-Authorization header even though it won't have any effect as the request is not using a forwarding proxy or a tunneling proxy. In those cases, urllib3 doesn't treat the Proxy-Authorization HTTP header as one carrying authentication material and thus doesn't strip the header on cross-origin redirects.

Because this is a highly unlikely scenario, we believe the severity of this vulnerability is low for almost all users. Out of an abundance of caution urllib3 will automatically strip the Proxy-Authorization header during cross-origin redirects to avoid the small chance that users are doing this on accident.

Users should use urllib3's proxy support or disable automatic redirects to achieve safe processing of the Proxy-Authorization header, but we still decided to strip the header by default in order to further protect users who aren't using the correct approach.

Affected usages

We believe the number of usages affected by this advisory is low. It requires all of the following to be true to be exploited:

  • Setting the Proxy-Authorization header without using urllib3's built-in proxy support.
  • Not disabling HTTP redirects.
  • Either not using an HTTPS origin server or for the proxy or target origin to redirect to a malicious origin.
Remediation
  • Using the Proxy-Authorization header with urllib3's ProxyManager.
  • Disabling HTTP redirects using redirects=False when sending requests.
  • Not using the Proxy-Authorization header.

Severity

  • CVSS Score: 4.4 / 10 (Medium)
  • Vector String: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

References

  • [https://github.com/urllib3/urllib3/security/advis

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⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

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The artifact failure details are included below:

File name: uv.lock
Using CPython 3.11.16
error: No solution found when resolving dependencies for split (markers: python_full_version >= '3.12')
  cause: Because opensearch-py<=1.0.0 depends on urllib3>=1.21.1,<2 and your project depends on opensearch-py==1.0.0, we can conclude that your project depends on urllib3>=1.21.1,<2.
         And because your project depends on urllib3==2.8.0, we can conclude that your project's requirements are unsatisfiable.

hint: While the active Python version is 3.11, the resolution failed for other Python versions supported by your project. Consider limiting your project's supported Python versions using `requires-python`.

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