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EUVD-2026-340364

fkie_cve-2026-65600

Traefik versions <= v2.11.51, >= v3.6.0 <= v3.6.22, and >= v3.7.0 <= v3.7.6 contain an authentication bypass via path traversal in the ReplacePathRegex middleware. When ReplacePathRegex is configured with a regex that captures user-controlled path segments without a mandatory path separator (e.g. regex "^/api(.*)", replacement "/$1"), the middleware forwards the replaced path to the backend without validating that it matches its normalized form. An unauthenticated remote attacker can send a crafted request (e.g. GET /api../admin) that produces an un-normalized path such as /../admin, which a backend that normalizes paths resolves to a protected route, bypassing authentication middleware. Fixed in v2.11.52, v3.6.23, and v3.7.7.

GHSA-cxjq-mrr5-89rv — Traefik: Authentication Bypass via Path Traversal in ReplacePathRegex Middleware

Affected: Go: github.com/traefik/traefik/v2, Go: github.com/traefik/traefik/v3, Go: github.com/traefik/traefik

## Summary

There is a critical authentication-bypass vulnerability in Traefik's `ReplacePathRegex` middleware. When it is configured with a regular expression that captures user-controlled path segments without a mandatory separator (for example `regex: "^/api(.*)"`, `replacement: "/$1"`), a crafted request can produce an un-normalized replacement path such as `/../admin`, which Traefik forwarded to the backend without validation. A backend that normalizes the path may resolve it to a protected route, letting an unauthenticated attacker reach resources located behind authentication middleware. This is the same class of issue that was fixed for `StripPrefix` in CVE-2026-48020; that post-replacement normalization check had not been applied to `ReplacePathRegex`. The fix rejects any request whose replaced path does not match its normalized form.

## Patches

- https://github.com/traefik/traefik/releases/tag/v2.11.52 - https://github.com/traefik/traefik/releases/tag/v3.6.23 - https://github.com/traefik/traefik/releases/tag/v3.7.7

## For more information

If you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).

<details> <summary>Original Description</summary>

### Summary A path traversal vulnerability in the ReplacePathRegex middleware allows an unauthenticated remote attacker to bypass authentication middleware and access protected routes by sending a single crafted HTTP request. The vulnerability exists b…

RHSA-2026:62260 — Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.30.0 Release.

netty: netty-codec-http2: Netty MadeYouReset HTTP/2 DDoS Vulnerability curl: curl: Insecure connection establishment due to TLS configuration mismatch shell-quote: shell-quote: Arbitrary code execution via command injection due to unescaped line terminators curl: curl: Man-in-the-middle attack via SSH host key bypass org.eclipse.parsson/parsson: Eclipse Parsson: Denial of Service via uncontrolled resource consumption in JSON parsing jetty-security: Eclipse Jetty: Authentication bypass via Digest authentication encoding collision jetty: Eclipse Jetty: Information disclosure due to retained HTTP/1.1 trailers across connections form-data: form-data: Form field override via CRLF injection undici: undici: Denial of Service due to unbounded memory growth via WebSocket frames brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity vertx-core: Eclipse Vert.x: Information disclosure via improper handling of HTTP 30x redirects io.vertx/vertx-web: Eclipse Vert.x Web Client: Information disclosure via improper cookie domain validation golang.org/x/net/html: golang: golang.org/x/net/html: Cross-Site Scripting via HTML parsing bypass github.com/go-jose/go-jose/v3: github.com/go-jose/go-jose/v4: Go JOSE: Denial of Service via crafted JSON Web Encryption (JWE) object net/mail: golang: Go net/mail: Denial of Service via crafted email inputs golang.org/x/crypto/ssh: golang.org/x/crypto/ssh: Security key bypass due to missing user presence check golang.org/x/cryp…