---
id: CVE-2026-88011
title: Traefik is an open source HTTP reverse proxy and load balancer
summary: >-
  Traefik is an open source HTTP reverse proxy and load balancer. Prior to
  2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such
  as X.Authenticated.User survives ForwardAuth replacement and
  underscoreHeadersStrategy …
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-290
vendor: traefik
product: traefik
affected:
  - traefik < 2.11.56
  - 'traefik >= 3.0.0, < 3.7.12'
patched:
  - traefik 3.7.12
published: '2026-09-10'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T15:17:24.163'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88011'
references:
  - url: >-
      https://github.com/traefik/traefik/commit/0331801c72329e0eaeb850e53ccce87c57fbecf8
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/pull/13720'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/releases/tag/v2.11.56'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/releases/tag/v3.7.12'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/security/advisories/GHSA-rf44-j88r-hh8c'
    label: security-advisories@github.com
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88011'
  - url: 'https://github.com/traefik/traefik'
tags:
  - nvd
  - cve.org
  - osv
  - go
  - score-dispute
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-15T14:42:09.176083Z'
scores:
  nvd: 8.1
  cna: 5.3
epss: 0.0042
epssPercentile: 0.33655
ingestedAt: '2026-09-11T10:30:26.778Z'
aliases:
  - GHSA-rf44-j88r-hh8c
  - CVE-2026-88879
  - GO-2026-6455
ecosystem: go
---

## Overview

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.

## Affected

- `traefik < 2.11.56`
- `traefik >= 3.0.0, < 3.7.12`

## Remediation

Upgrade past the affected range:

- `traefik 3.7.12`

## Package advisory (CVE-2026-88011)

Affected packages:

- `github.com/traefik/traefik/v2 < 2.11.56`
- `github.com/traefik/traefik/v3 >= 3.0.0, < 3.7.12`

Patched in:

- `github.com/traefik/traefik/v2 2.11.56`
- `github.com/traefik/traefik/v3 3.7.12`

Source: https://osv.dev/vulnerability/GHSA-rf44-j88r-hh8c