GHSA-29VQ-49WR-VM6X

Vulnerability from github – Published: 2026-02-19 20:32 – Updated: 2026-02-23 22:27
VLAI
Summary
Werkzeug safe_join() allows Windows special device names
Details

Werkzeug's safe_join function allows Windows device names as filenames if when preceded by other path segments.

This was previously reported as https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL.

send_from_directory uses safe_join to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.

Severity
6.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "werkzeug"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.1.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27199"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-67"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-19T20:32:45Z",
    "nvd_published_at": "2026-02-21T06:17:00Z",
    "severity": "MODERATE"
  },
  "details": "Werkzeug\u0027s `safe_join` function allows Windows device names as filenames if when preceded by other path segments.\n\nThis was previously reported as https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that `safe_join` accepts paths with multiple segments, such as `example/NUL`.\n\n`send_from_directory` uses `safe_join` to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely.",
  "id": "GHSA-29vq-49wr-vm6x",
  "modified": "2026-02-23T22:27:37Z",
  "published": "2026-02-19T20:32:45Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27199"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/pallets/werkzeug"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pallets/werkzeug/releases/tag/3.1.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": " Werkzeug safe_join() allows Windows special device names"
}


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