CVE-2019-20894 Improper Authentication

What is CVE-2019-20894?

CVE-2019-20894 is a high-severity vulnerability in Traefik Traefik, published on 2 Jul 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Traefik 2.x, in certain configurations, allows HTTPS sessions to proceed without mutual TLS verification in a situation where ERR_BAD_SSL_CLIENT_AUTH_CERT should have occurred.

Weakness: CWE-295

Which versions are affected by CVE-2019-20894?

4 open source packages ship an affected version, including github.com/traefik/traefik/v2, github.com/containous/traefik and github.com/containous/traefik/v2. It affects 1 product.

Products include Traefik Traefik.

How do I fix CVE-2019-20894?

Upgrade github.com/traefik/traefik/v2 to 2.2.2 or later.

Is CVE-2019-20894 being exploited?

There is no known exploitation of CVE-2019-20894 in the wild and no public exploit code.

Other vulnerabilities in Traefik Traefik

• CVE-2024-45410 HTTP client can remove the X-Forwarded headers in Traefik Critical 9.8
• CVE-2026-88877 Traefik v3.7.0 Authentication Bypass via from-to-www-redirect Critical 9.3
• CVE-2026-85595 Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth Critical 9.3
• CVE-2026-88007 Traefik HTTP/3 Backend NTLM Connection Reuse Critical 9.1
• CVE-2026-88009 Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging High 8.8

All Traefik Traefik vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-q9mp-79cp-9g8j, GO-2022-0774.