Medium 6.3Published Feb 21, 2026

CVE-2026-27199Werkzeug safe_join() allows Windows special device names

Updated under an hour ago (Oct 27, 2026, 3:23 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 6.3 MEDIUM (v4.0, CNA)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
Weakness (CWE): CWE-67
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Feb 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pallets werkzeug pallets:werkzeug (from the name)	before 3.1.6	CNA record
palletsprojects werkzeug palletsprojects:werkzeug	before 3.1.6	NVD

References

References

https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x	x-refsource-confirm, vendor-advisory
https://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d	x-refsource-misc, patch
https://github.com/pallets/werkzeug/releases/tag/3.1.6	x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.