Path Traversal in Traefik

CVE-2026-40912

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's StripPrefixRegex middleware when used in combination with ForwardAuth, BasicAuth, or DigestAuth. The middleware matches the regex against the decoded URL path but uses the resulting byte length to slice the percent-encoded raw path. When a dot (or multiple dots) appears 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 X-Forwarded-Uri, which does not match the protected path patterns and therefore allows the request through. The backend then normalizes the dot-segment to the real path per RFC 3986 and serves the protected content An unauthenticated attacker can exploit this against any backend that performs dot-segment normalization. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (53.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-40912: held from 0.008 to 0.007.

EPSS over last 30 days · oldest: 0.008 · newest: 0.007 · change: -0.000

Affected products

  • Traefik — versions 3.7.0, >= 3.0.0-beta1, < 3.6.14, < 2.11.43

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-40912?
CVE-2026-40912 is a high-severity vulnerability in Traefik, classified under Use of Incorrectly-Resolved Name or Reference. CVSS score: 8.2/10. Published 2026-04-30.
How severe is CVE-2026-40912?
High severity. CVSS v3 base score is 8.2 out of 10.