# CVE-2026-40912: Traefik: StripPrefixRegex auth bypass via Path/RawPath desync > An unauthenticated attacker can bypass authentication in Traefik by exploiting a path desync in StripPrefixRegex, allowing access to protected backend content. - **Severity:** High 7.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 30 Apr 2026 - **Updated:** 15 Jul 2026 - **Also known as:** CLEANSTART-2026-FP02256, GHSA-6jwx-7vp4-9847, GO-2026-5180, MINI-298w-j8fg-2vcg, MINI-5rc8-ch82-76wr, MINI-j5xm-6hhx-jr2q ## What is CVE-2026-40912? CVE-2026-40912 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), CWE-706 (Use of Incorrectly-Resolved Name or Reference) ## Which versions are affected by CVE-2026-40912? 11 open source packages ship an affected version, including github.com/traefik/traefik/v3, github.com/traefik/traefik and github.com/traefik/traefik/v2. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/traefik/traefik/v3` | Go | From 3.0.0-beta1 | 3.6.14, 3.7.0-rc.2 | | `github.com/traefik/traefik/v3` | Go | From 3.0.0-beta1 | 3.6.14 | | `github.com/traefik/traefik/v3` | Go | From 3.0.0-beta1 | 3.6.14 | | `github.com/traefik/traefik/v3` | Go | From 3.7.0-ea.1 | 3.7.0-rc.2 | | `github.com/traefik/traefik/v3` | Go | From 3.7.0-ea.1 | 3.7.0-rc.2 | | `github.com/traefik/traefik` | Go | All versions | None | | `github.com/traefik/traefik` | Go | All versions to 1.7.34 | None | | `github.com/traefik/traefik` | Go | All versions to 1.7.34 | None | | `github.com/traefik/traefik/v2` | Go | All versions | 2.11.43 | | `github.com/traefik/traefik/v2` | Go | All versions | 2.11.43 | | `github.com/traefik/traefik/v2` | Go | All versions | 2.11.43 | Products: Traefik Traefik. ## How do I fix CVE-2026-40912? Upgrade github.com/traefik/traefik/v3 to a fixed version for your release line: 3.6.14 or 3.7.0-rc.2. ## Is CVE-2026-40912 being exploited? There is no known exploitation of CVE-2026-40912 in the wild and no public exploit code. ## Other vulnerabilities in Traefik Traefik - [CVE-2024-45410](https://insights.sbomify.com/CVE-2024-45410/): HTTP client can remove the X-Forwarded headers in Traefik (critical 9.8) - [CVE-2026-88877](https://insights.sbomify.com/CVE-2026-88877/): Traefik v3.7.0 Authentication Bypass via from-to-www-redirect (critical 9.3) - [CVE-2026-85595](https://insights.sbomify.com/CVE-2026-85595/): Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth (critical 9.3) - [CVE-2026-88007](https://insights.sbomify.com/CVE-2026-88007/): Traefik HTTP/3 Backend NTLM Connection Reuse (critical 9.1) - [CVE-2026-88009](https://insights.sbomify.com/CVE-2026-88009/): Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging (high 8.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-40912 and fix it if it is affected. What it is: CVE-2026-40912 is a high-severity authentication bypass vulnerability in Traefik Traefik, published on 30 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-40912 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/traefik/traefik/v3 (Go): affected from 3.0.0-beta1; fixed in 3.6.14, 3.7.0-rc.2 - github.com/traefik/traefik/v3 (Go): affected from 3.0.0-beta1; fixed in 3.6.14 - github.com/traefik/traefik/v3 (Go): affected from 3.0.0-beta1; fixed in 3.6.14 - github.com/traefik/traefik/v3 (Go): affected from 3.7.0-ea.1; fixed in 3.7.0-rc.2 - github.com/traefik/traefik/v3 (Go): affected from 3.7.0-ea.1; fixed in 3.7.0-rc.2 - github.com/traefik/traefik (Go): affected all versions; no fix listed - github.com/traefik/traefik (Go): affected all versions up to 1.7.34; no fix listed - github.com/traefik/traefik (Go): affected all versions up to 1.7.34; no fix listed - github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.43 - github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.43 - github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.43 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-40912/ (Markdown: https://insights.sbomify.com/CVE-2026-40912/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40912 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40912 - OSV: https://osv.dev/vulnerability/CVE-2026-40912 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-40912/ Summaries are generated and may contain mistakes; the official description above is the record.