---
id: CVE-2026-85597
title: >-
  Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option
  conflict resolution vulnerability that allows unauthenticated attackers to
  bypass client-certificate authentication by creating conflicting TLS options
  on multi-host…
summary: >-
  Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option
  conflict resolution vulnerability that allows unauthenticated attackers to
  bypass client-certificate authentication by creating conflicting TLS options
  on multi-host…
severity: critical
cvss: 9.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-863
  - CWE-303
vendor: traefik
product: traefik
affected:
  - traefik < 2.11.55
  - 'traefik >= 3.0.0, < 3.7.11'
patched:
  - traefik 3.7.11
published: '2026-09-04'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:42:21.680'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-85597'
references:
  - url: 'https://github.com/traefik/traefik/security/advisories/GHSA-g55h-rg46-x9c5'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/traefik-before-2.11.55-mtls-bypass-via-tls-option-conflict
    label: disclosure@vulncheck.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-85597.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-85597'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2528835'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-85597'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-85597'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
epss: 0.00205
epssPercentile: 0.10763
scores:
  nvd: 9.1
  vendor: 7.5
ingestedAt: '2026-09-06T01:47:57.962Z'
---

## Overview

Traefik before v2.11.55 and v3.0.0 through v3.7.10 contain a TLS option conflict resolution vulnerability that allows unauthenticated attackers to bypass client-certificate authentication by creating conflicting TLS options on multi-host routers. Attackers can reach protected backends by exploiting shared TLS resolution across multiple hostnames in a single router rule, causing the strict mTLS requirement to fall back to default options for all hosts.

## Affected

- `traefik < 2.11.55`
- `traefik >= 3.0.0, < 3.7.11`

## Remediation

Upgrade past the affected range:

- `traefik 3.7.11`

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat OpenShift Dev Spaces · no fix planned: Red Hat OpenShift Dev Spaces · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-85597.json)