high CVSS 8.7

CVE-2026-114642·Traefik vulnerability

Traefik 2.11.0 before 2.11.58 and 3.0.0 before 3.7.14 stores its NTLM/Kerberos backend round tripper in a client-connection slot not keyed by ServersTransport, so one service's TLS client configuration is reused for another service's backend. An unauthenticated client can arm the slot via a backend issuing an NTLM or Negotiate challenge, then reach another service on the same keep-alive connection, bypassing its root CAs, server name, and certificate verification.

Severity
high
Software
Traefik
Fixed in
3.7.14
Published

Affected versions

From: 3.0.0

Until: 3.7.14

Fixed in: 3.7.14

How to fix this CVE

Upgrade Traefik immediately to version 2.11.58 or later (3.7.14+ for v3 deployments) to patch a critical TLS configuration bypass affecting NTLM and Kerberos authentication flows. This vulnerability allows attackers to reuse TLS client certificates and bypass certificate verification across different backend services on the same connection. Deploy the patched version and restart all Traefik instances to ensure the fix is active.

sudo dnf update traefik

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET .* HTTP/1\.1.*(?:WWW-Authenticate: Negotiate|WWW-Authenticate: NTLM).*Connection: keep-alive.*followed by request to different Host header on same connection

How to check if you are affected

  1. Check installed Traefik version: traefik version or docker inspect $(docker ps -q -f ancestor=traefik) | grep -i version
  2. Verify if NTLM or Kerberos backends are configured: grep -r 'NTLM\|Negotiate\|Kerberos' /etc/traefik/ or check your traefik.yml/toml for auth-forwardauth middleware with these schemes
  3. Search Traefik access logs for repeated TLS handshake errors or certificate verification failures followed by requests to different backend services on the same connection: grep -E 'TLS|certificate|peer' /var/log/traefik/access.log
  4. Confirm fix application by verifying version is ≥2.11.58 (v2) or ≥3.7.14 (v3): traefik version and cross-check against the fixed versions in your deployment

FAQ

What is CVE-2026-114642?

This CVE describes a TLS client configuration reuse flaw in Traefik where NTLM/Kerberos authentication credentials cached in a keep-alive connection slot can be replayed to bypass certificate verification when reaching different backend services. An attacker can exploit this to access services with forged or missing certificate validation.

Is CVE-2026-114642 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploit code is currently available, though the attack requires network access to a Traefik instance configured with NTLM or Kerberos backends.

What versions of Traefik are affected by CVE-2026-114642?

Traefik 2.11.0 through 2.11.57 and 3.0.0 through 3.7.13 are vulnerable. Versions 2.11.58 and 3.7.14 (and later) include the fix.

How do I check if my server is vulnerable to CVE-2026-114642?

Run 'traefik version' and compare the version number against the vulnerable ranges above. If you are running 2.11.x (before 2.11.58) or 3.x (before 3.7.14), your instance is vulnerable if NTLM or Kerberos authentication is enabled on any backend.

Does Defensia detect CVE-2026-114642?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-114642 will appear in your dashboard with remediation steps.

Related Traefik CVEs

CVE-2026-48491CVSS 10Traefik is an HTTP reverse proxy and load balancer. From 3.7.0 until 3.7.3, there is a high severity vulnerability in Traefik's domain-fronting protection (SNICheck) that allows an unauthenticated client to bypass mutual TLS enforced through wildcard router TLSOptions. When a router uses a wildcard host rule such as Host(*.example.com) with stricter TLS options (for example RequireAndVerifyClientCert), SNICheck resolves the TLS options for the HTTP Host header using exact map lookups only and never applies wildcard matching. If another permissive SNI is served on the same entrypoint, an attacker can complete the TLS handshake under the permissive options and then send an HTTP Host header targeting the wildcard-protected backend, reaching it without presenting a client certificate. This affects the regular HTTPS / HTTP-2 path and does not require HTTP/3. This vulnerability is fixed in 3.7.3.
CVE-2026-54763CVSS 10Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth, DigestAuth, and ForwardAuth middlewares strip canonical-cased spoofed identity headers before writing Traefik's own value, but do not account for underscore-variant header names, which many backends normalize identically to dashed forms. An attacker able to reach a protected route can inject an underscore-variant header that survives Traefik's stripping and reaches the backend alongside, or on the unauthenticated ForwardAuth authResponseHeaders path instead of, the value Traefik intended to set, spoofing identity or authorization context. This issue is fixed in versions v2.11.51, v3.6.22, and v3.7.6.
CVE-2026-53622CVSS 10Traefik is an HTTP reverse proxy and load balancer. Versions prior to 3.7.3, 3.6.18, and 2.11.51 have a critical vulnerability in Traefik's HTTP/3 (QUIC) TLS configuration selection that allows unauthenticated clients to bypass router-specific mTLS enforcement. When HTTP/3 is enabled on an entrypoint, the TLS handshake selects the applicable TLS configuration through an exact, case-sensitive lookup on the SNI value, which fails to match wildcard host patterns (e.g., *.example.com) or case variants of the configured hostname. Because the handshake falls back to the default TLS configuration — which may not require client certificates — a client can complete the QUIC handshake without presenting a certificate, while the subsequent HTTP routing layer still dispatches the request to a backend protected by a router-specific mTLS policy. The issue affects deployments where HTTP/3 is enabled, a router uses a wildcard Host rule or case-insensitive hostname matching, a router-specific TLSOptions enforces client certificate authentication, and UDP access to the entrypoint is reachable by an attacker. This vulnerability is fixed in versions 3.7.3, 3.6.18, and 2.11.51.
CVE-2026-48020CVSS 10Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.48, 3.6.19, and 3.7.3, there is a high severity vulnerability in Traefik's StripPrefix middleware that allows an unauthenticated attacker to bypass route-level authentication and authorization. When a public router matches on a PathPrefix rule and applies the StripPrefix middleware, a request path containing .. or its percent-encoded form %2e%2e can match the public route at routing time and then, after the prefix is stripped and the path is normalized, resolve to a path served by a separate, authenticated router. As a result, an attacker can reach protected backend paths — such as admin or internal configuration endpoints — without satisfying the authentication middleware attached to the protected router. This vulnerability is fixed in 2.11.48, 3.6.19, and 3.7.3.
CVE-2026-44774CVSS 9.9Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.46, 3.6.17, and 3.7.1, Traefik's Kubernetes Gateway API provider allows a tenant with HTTPRoute creation permissions to expose the REST provider handler, bypassing the providers.rest.insecure=false setting. The Gateway provider accepts any TraefikService backend reference whose name ends with @internal, making it possible to route traffic to rest@internal in addition to the intended api@internal. In shared Gateway deployments where the REST provider is enabled, this allows a low-privileged actor to gain live dynamic configuration write access to Traefik, enabling unauthorized reconfiguration of routers and services. This vulnerability is fixed in 2.11.46, 3.6.17, and 3.7.1.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2026-114642. Free for 1 server.

Get started free