What’s Vulnerable › Vulnerabilities

CVE-2026-85597: Traefik before v2.11.55 and v3.0.0 through v3.7.10 mTLS Bypass via TLS Option Conflict

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-09-04 · updated 2026-10-08
• Weakness: CWE-863

Description

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 products

• Traefik: before 2.11.55; from 3.0.0 before 3.7.11 — fixed in 2.11.55, 3.7.11

How to fix

Upgrade to a fixed version: Traefik 2.11.55, 3.7.11. Check the vendor advisory for mitigations.

References

• https://github.com/traefik/traefik/security/advisories/GHSA-g55h-rg46-x9c5
• https://www.vulncheck.com/advisories/traefik-before-2.11.55-mtls-bypass-via-tls-option-conflict

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