high CVSS 8.7 EPSS 0.31%

CVE-2026-114639·Traefik vulnerability

Traefik 2.11.0 before 2.11.58 and 3.0.0 before 3.7.14 contains an authentication bypass because a first request preauthenticated with an Authorization: Negotiate token authenticates a socket in the globally shared backend connection pool, which is never isolated. Unauthenticated attackers on separate frontend connections can be assigned that NTLM/Kerberos-bound socket and perform reads or writes with the victim's identity.

Severity
high
Software
Traefik
Fixed in
3.7.14
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.31% — higher than 23% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-114639 scores 8.7 on CVSS, so a successful attack would be serious — but at 0.31%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

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 users) to patch a critical authentication bypass flaw in the connection pooling mechanism. The vulnerability allows attackers to hijack authenticated backend connections previously established by legitimate users, potentially gaining unauthorized access to protected resources. Apply the update during a maintenance window and restart Traefik services to ensure the patched code is loaded.

sudo dnf check-update traefik && sudo dnf install -y traefik-2.11.58

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

Regex pattern: (Authorization:\s*Negotiate\s+[A-Za-z0-9+/=]+).*followed within 5 seconds by a request from a different source IP accessing the same backend service, or HTTP 401 -> HTTP 200 sequence without re-authentication headers

WAF mitigation (if patching is not yet possible)

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

Implement request-level rate limiting on Authorization: Negotiate endpoints and enforce strict session affinity (sticky sessions) to prevent connection pool hijacking. Add WAF rules to block requests that mix Negotiate tokens across different client IP addresses within the same backend pool window.

How to check if you are affected

  1. Run 'traefik version' or check the Docker image tag to determine the installed Traefik version; compare against 2.11.58 (v2) or 3.7.14 (v3) thresholds
  2. Examine Traefik configuration files for active NTLM or Kerberos authentication middleware; check if 'ForwardAuth' or 'BasicAuth' with Negotiate tokens are enabled
  3. Search Traefik access logs for Authorization: Negotiate headers followed by unexpected backend operations from different source IPs within the same session window
  4. After upgrading, verify the running version with 'traefik version' and confirm no lingering NTLM-bound sockets by monitoring backend connection pool metrics in the dashboard

FAQ

What is CVE-2026-114639?

This vulnerability is a connection pool reuse flaw in Traefik's reverse proxy that allows unauthenticated attackers to steal pre-authenticated NTLM/Kerberos-bound sockets from the global backend connection pool. An attacker can inject a new frontend request into a socket originally authenticated by another user, inheriting their identity and permissions.

Is CVE-2026-114639 being actively exploited?

As of the latest intelligence, CVE-2026-114639 is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploit code has been disclosed, though the vulnerability is highly impactful and should be treated as an urgent priority.

What versions of Traefik are affected by CVE-2026-114639?

Traefik versions 2.11.0 through 2.11.57 and 3.0.0 through 3.7.13 are vulnerable. Fixed versions are 2.11.58 and 3.7.14 or later.

How do I check if my server is vulnerable to CVE-2026-114639?

Run 'traefik version' and compare the output against fixed versions 2.11.58 or 3.7.14. For containerized deployments, inspect the image tag with 'docker inspect {image_id} | grep -i version'. If your version is below the fixed threshold, your instance is vulnerable.

Does Defensia detect CVE-2026-114639?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Traefik is installed on a monitored server, CVE-2026-114639 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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