This release includes 10 security fixes following the security policy: - x/mod/sumdb/tlog: fix transparency log tile verification bypass A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that cannot be detected by evaluating the transparency log. All tiles are now correctly verified against their parents. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy Thanks to Filippo Valsorda (Geomys) for reporting this issue. This is CVE-2026-56865 and Go issue https://go.dev/issue/80744. - x/mod/sumdb: ignore unrelated, unauthenticated hashes in Lookup A malicious GOSUMDB was capable of serving arbitrary module content not contained within the transparency log. This attack allows for a coordinating GOPROXY and GOSUMDB to serve a client malicious module content that cannot be detected by evaluating the transparency log. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy Thanks to mundur for reporting this issue. This is CVE-2026-56864 and Go issue https://go.dev/issue/80745. - encoding/xml: add recursion depth guard during decode Previously, DecodeElement would reset the depth counter causing it to never fire; this could lead to stack exhaustion. This is CVE-2026-56859 and Go issue https://go.dev/issue/80481. net/http: apply ReadHeaderTimeout when doing unencrypted HTTP/2 check When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. Previously, this was being done with no timeout applied. ReadHeaderTimeout is now applied for this. This is CVE-2026-56853 and Go issue https://go.dev/issue/80205. - net/url: avoid quadratic complexity in resolvePath Previously, resolving relative paths containing parent directory (..) segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. Now, path resolution operates on a byte buffer using index-based backtracking for .. segments, eliminating the quadratic time complexity and significantly reducing memory allocations. This is CVE-2026-56860 and Go issue https://go.dev/issue/80494. - golang.org/x/net/dns/dnsmessage: panic when parsing invalid SVCB record Parsing an invalid SVCB or HTTPS RR can panic when the size of a parameter value overflows the message buffer. Thanks to Mundur (https://github.com/M0nd0R) for reporting this issue. This is CVE-2026-46600 and Go issue https://go.dev/issue/79795. - crypto/tls: limit handshake messages we are willing to accept post-handshake Previously, we always counted handshake messages, such as KeyUpdate, as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely. Thanks to Qi Deng of Aurascape.ai for reporting this issue. This is CVE-2026-56862 and Go issue https://go.dev/issue/80528. - html/template: fix Javascript regexp context tracking Previously, pathological inputs could close an unescaped / early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS. Thanks to Ali Sherif for reporting this issue. This is CVE-2026-56858 and Go issue https://go.dev/issue/80435. - x/net/idna: failure to reject ASCII-only Punycode-encoded labels The ToASCII and ToUnicode functions incorrectly accepted Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returned the name "example.com" rather than an error. The idna package implements the processing algorithm from UTS 46. Older versions of UTS 46 included a specification bug which permitted multiple ASCII labels to decode to the same Unicode label. UTS 46 revision 33 fixed the specification bug. The idna package now implements the updated specification. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject "example.com" but permit "xn--example-.com". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name "example.com". Thanks to KC1zs4 (https://github.com/KC1zs4) for reporting this issue. This is CVE-2026-39821 and Go issue https://go.dev/issue/78760. - encoding/asn1: enforce maximum recursion depth Enforce a recursion limit in Unmarshal to prevent stack exhaustion when parsing deeply-nested, recursive structures. Thanks to Marwan Atia (marwans...@gmail.com) for reporting this issue. This is CVE-2026-33818 and Go issue https://go.dev/issue/80405. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Commits

Commits on Aug 14, 2026

update to go1.26.6