Publish GHSA-x8cg-fq8g-mxfx

Author: advisory-database[bot]

advisories/github-reviewed/2026/04/GHSA-x8cg-fq8g-mxfx/GHSA-x8cg-fq8g-mxfx.json

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+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-x8cg-fq8g-mxfx",
+  "modified": "2026-04-02T19:07:28Z",
+  "published": "2026-04-02T19:07:28Z",
+  "aliases": [
+    "CVE-2026-34826"
+  ],
+  "summary": "Rack's multipart byte range processing allows denial of service via excessive overlapping ranges",
+  "details": "## Summary\n\n`Rack::Utils.get_byte_ranges` parses the HTTP `Range` header without limiting the number of individual byte ranges. Although the existing fix for CVE-2024-26141 rejects ranges whose total byte coverage exceeds the file size, it does not restrict the count of ranges. An attacker can supply many small overlapping ranges such as `0-0,0-0,0-0,...` to trigger disproportionate CPU, memory, I/O, and bandwidth consumption per request.\n\nThis results in a denial of service condition in Rack file-serving paths that process multipart byte range responses.\n\n## Details\n\n`Rack::Utils.get_byte_ranges` accepts a comma-separated list of byte ranges and validates them based on their aggregate size, but does not impose a limit on how many individual ranges may be supplied.\n\nAs a result, a request such as:\n\n```http\nRange: bytes=0-0,0-0,0-0,0-0,...\n```\n\ncan contain thousands of overlapping one-byte ranges while still satisfying the total-size check added for CVE-2024-26141.\n\nWhen such a header is processed by Rack’s file-serving code, each range causes additional work, including multipart response generation, per-range iteration, file seek and read operations, and temporary string allocation for response size calculation and output. This allows a relatively small request header to trigger disproportionately expensive processing and a much larger multipart response.\n\nThe issue is distinct from CVE-2024-26141. That fix prevents range sets whose total byte coverage exceeds the file size, but does not prevent a large number of overlapping ranges whose summed size remains within that limit.\n\n## Impact\n\nApplications that expose file-serving paths with byte range support may be vulnerable to denial of service.\n\nAn unauthenticated attacker can send crafted `Range` headers containing many small overlapping ranges to consume excessive CPU time, memory, file I/O, and bandwidth. Repeated requests may reduce application availability and increase pressure on workers and garbage collection.\n\n## Mitigation\n\n* Update to a patched version of Rack that limits the number of accepted byte ranges.\n* Reject or normalize multipart byte range requests containing excessive range counts.\n* Consider disabling multipart range support where it is not required.\n* Apply request filtering or header restrictions at the reverse proxy or application boundary to limit abusive `Range` headers.",
+  "severity": [
+    {
+      "type": "CVSS_V3",
+      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "RubyGems",
+        "name": "rack"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "0"
+            },
+            {
+              "fixed": "2.2.23"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "package": {
+        "ecosystem": "RubyGems",
+        "name": "rack"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "3.0.0.beta1"
+            },
+            {
+              "fixed": "3.1.21"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "package": {
+        "ecosystem": "RubyGems",
+        "name": "rack"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "3.2.0"
+            },
+            {
+              "fixed": "3.2.6"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/rack/rack/security/advisories/GHSA-x8cg-fq8g-mxfx"
+    },
+    {
+      "type": "ADVISORY",
+      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34826"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/rack/rack"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-400",
+      "CWE-770"
+    ],
+    "severity": "MODERATE",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-04-02T19:07:28Z",
+    "nvd_published_at": "2026-04-02T17:16:25Z"
+  }
+}