CVE-2026-40912: Traefik: StripPrefixRegex auth bypass via Path/RawPath desync
Vulnerability summary
CVE-2026-40912 is a high (CVSS 8.6) vulnerability in traefik. EPSS estimates a 0.77% chance of exploitation in the next 30 days, higher than 55.5% of scored vulnerabilities. 1 public exploit is recorded.
Public exploit (GitHub, Date unknown)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 3 · Related 3Timeline
- 30-04-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
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.
CVSS metrics
7 scores · 4 sources · 2 versions- OSV · GoEcosystem advisory · calculated7.8HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N
- OSV · ChainguardEcosystem advisory · calculated7.8HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N
- NVDNIST7.8HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · GoEcosystem advisory · calculated8.2HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:NDiffers
- NVDNIST8.2HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:NDiffers
EPSS trend
Probability
0.77%
Chance of exploitation in the next 30 days
Percentile
56%
Versus all other CVEs
30-day change
Increase +0.05 pp
From 0.72% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundTraefik
Maturity: poc
Weaknesses
CWE · root cause- CWE-706Use of Incorrectly-Resolved Name or ReferenceThe product uses a name or reference to access a resource, but the name/reference resolves to a resource that is outside of the intended control sphere.
- CWE-22Improper Limitation of a Pathname to a Restricted DirectoryThe product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Affected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard2 products
- traefik-3.5All versions (No fix recorded)
- traefik-fips-3.5All versions (No fix recorded)
Github.com/traefik/traefik2 products
- v2< 2.11.43
- v3≥ 3.0.0-beta1, < 3.6.14 | ≥ 3.7.0-ea.1, < 3.7.0-rc.2
Github.com/traefik1 product
- traefik≤ 1.7.34 | All versions (No fix recorded)
Traefik1 product
- traefik≥ 3.0.0-beta1, < 3.6.14 | ≥ 3.7.0-ea.1, < 3.7.0-rc.2 | < 2.11.43 | ≥ 3.0.0, < 3.6.14 | 3.7.0:ea1 | 3.7.0:ea2 | 3.7.0:ea3 | 3.7.0:rc1
4 vendors · 6 products
References
11 links- github.com/traefik/traefik/security/advisories/GHSA-6jwx-7vp4-9847X Refsource CONFIRMWEBAdvisoryExploitPatchVendor Advisory
- github.com/traefik/traefikPACKAGE