CVE-2026-27199

Name	CVE-2026-27199
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-werkzeug (PTS)	bullseye	1.0.1+dfsg1-2+deb11u1	fixed
	bullseye (security)	1.0.1+dfsg1-2+deb11u2	fixed
	bookworm	2.2.2-3+deb12u1	fixed
	trixie	3.1.3-2	fixed
	forky, sid	3.1.5-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
python-werkzeug	source	(unstable)	(not affected)

Notes

- python-werkzeug <not-affected> (Only affects werkzeug on Windows)
https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x
Fixed by: https://github.com/pallets/werkzeug/commit/f54fe98026253e70fbbcd35a6b52fb67cfff1c03 (3.1.6)