Auth bypass in Traefik
CVE-2026-85597
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (27.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 27.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.001
Affected products
Weakness classification (CWE)
References
- github.com/traefik/traefik/security/advisories/GHSA-g55h-rg46-x9c5 (Exploit, vendor-advisory, Patch, Mitigation, Vendor Advisory)
- www.vulncheck.com/advisories/traefik-before-2.11.55-mtls-bypass-via-tls-option-… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-85597?
- CVE-2026-85597 is a critical-severity vulnerability in Traefik, classified under Incorrect Authorization. CVSS score: 9.1/10. Published 2026-09-04.
- How severe is CVE-2026-85597?
- Critical severity. CVSS v3 base score is 9.1 out of 10.