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🛡️ CVE-2026-27199 on Alpine — py3-werkzeug

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as 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. The function 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. This issue has been fixed in version 3.1.6.

Distribution advisory

This page covers CVE-2026-27199 as tracked by Alpine, for the package py3-werkzeug. The fix is available in version 3.1.6-r0; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability low.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: Low — limited, and the attacker does not choose what is affected.

Weakness class

ALPINE-CVE-2026-27199 is classified as CWE-67: Improper Handling of Windows Device Names. The product constructs pathnames from user input, but it does not handle or incorrectly handles a pathname containing a Windows device name such as AUX or CON.

Affected software

ALPINE-CVE-2026-27199 is recorded against 1 package.

  • py3-werkzeug (fixed in 3.1.6-r0)

Timeline and source

Published on 21 February 2026 and last revised on 15 June 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security.alpinelinux.org (Advisory)

Other advisories for this package

py3-werkzeug has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-67: Improper Handling of Windows Device Names) in other software:

CVE-2026-27199 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-02-21
Updated 2026-08-20
Modified 2026-06-15
Fix URL N/A

Affected Packages

Software From version Fixed in
py3-werkzeug — 3.1.6-r0

Vulnerability Monitoring

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