PT-2026-36179 · Traefik · Traefik

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CVE-2026-40912

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Published

2026-04-22

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Updated

2026-07-30

CVSS v3.1

8.6

High

VectorAV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Name of the Vulnerable Software and Affected Versions Traefik versions prior to 2.11.43 Traefik versions prior to 3.6.14 Traefik versions prior to 3.7.0-rc.2
Description An authentication bypass exists in the StripPrefixRegex middleware when used with ForwardAuth, BasicAuth, or DigestAuth. The middleware matches a regular expression against the decoded URL path but applies the resulting byte length to slice the percent-encoded raw path. If a dot or multiple dots are present in the prefix portion of the URL, the raw path after stripping becomes a dot-segment (e.g., /./admin/secret). ForwardAuth receives this dot-segment path in the X-Forwarded-Uri variable, which fails to match protected path patterns, allowing the request to pass. The backend then normalizes the dot-segment to the actual path according to RFC 3986 and serves the protected content. This can be exploited by an unauthenticated attacker against any backend that performs dot-segment normalization.
Recommendations Update to version 2.11.43. Update to version 3.6.14. Update to version 3.7.0-rc.2.

Exploit

Fix

Path traversal

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Weakness Enumeration

Related Identifiers

BDU:2026-06476
CVE-2026-40912
GHSA-6JWX-7VP4-9847
GO-2026-5180
OPENSUSE-SU-2026:10697-1
OPENSUSE-SU-2026:10698-1
OPENSUSE-SU-2026:21483-1

Affected Products

Traefik