high CVSS 8.7

CVE-2026-114635·Traefik vulnerability

Traefik before v2.11.58 and v3.7.14 contains an authentication bypass vulnerability in its SNI check, which is skipped when request TLS state is nil. Unauthenticated clients can send HTTP/2 requests with the :scheme http pseudo-header over TLS on Go 1.27 builds to reach routers requiring client certificates without presenting one.

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 to version 3.7.14 or later to patch the SNI validation bypass that allows unauthenticated clients to bypass client certificate requirements. Organizations running versions 3.0.0 through 3.7.14 should prioritize this update, particularly if their infrastructure relies on mutual TLS authentication for access control. After upgrading, verify that SNI checks are properly enforced on all TLS connections.

sudo dnf update traefik

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

HTTP/2 requests with ':scheme http' pseudo-header received over TLS connections to port 443 or custom HTTPS entry points, combined with missing or invalid client certificate chains, followed by successful routing to protected backends

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement WAF rules to enforce strict HTTP/2 scheme validation: block any HTTP/2 requests with ':scheme http' arriving on HTTPS-only entry points; monitor and alert on protocol mismatches between the transport layer (TLS) and application-layer scheme declarations

How to check if you are affected

  1. Check installed version: traefik version | grep -oP 'Version=\K[^,]+' or docker inspect $(docker ps -q --filter 'ancestor=traefik:latest') | grep -i version
  2. Verify TLS entry points are configured: grep -A 10 'entryPoints' /etc/traefik/traefik.yml | grep -E '(tls|clientAuth)' to confirm client certificate requirements are set
  3. Search logs for HTTP/2 requests with :scheme pseudo-header mismatches: grep -i ':scheme http' /var/log/traefik/access.log | grep -v 'status.*[23][0-9][0-9]' to identify anomalous patterns
  4. Confirm the fix: traefik version | grep -E '(3\.7\.14|3\.[8-9]|[4-9]\.)' to ensure patched version is running

FAQ

What is CVE-2026-114635?

This vulnerability is an SNI (Server Name Indication) check bypass in Traefik that allows attackers to send specially crafted HTTP/2 requests over TLS without presenting required client certificates, effectively circumventing mutual TLS authentication policies that protect sensitive backends.

Is CVE-2026-114635 being actively exploited?

No, this vulnerability is not currently listed on CISA's KEV (Known Exploited Vulnerabilities) catalog, and no public exploit code has been released. However, the attack method is straightforward for skilled threat actors targeting environments with strict mTLS policies.

What versions of Traefik are affected by CVE-2026-114635?

Traefik versions 3.0.0 through 3.7.13 are vulnerable. Version 2.11.57 and earlier in the v2 branch are also affected. The fix is available in v3.7.14 and later, and v2.11.58 and later.

How do I check if my server is vulnerable to CVE-2026-114635?

Run 'traefik version' and compare the reported version against the vulnerable ranges (3.0.0–3.7.13 or 2.0.0–2.11.57). If your version falls within these ranges and you have TLS entry points configured with client authentication, your deployment is vulnerable.

Does Defensia detect CVE-2026-114635?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-114635 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

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