DEV Community

CVE Reports
CVE Reports

Posted on • Originally published at cvereports.com

CVE-2026-25949: Traefik's Eternal Wait: Bypassing TCP Timeouts with Postgres Magic Bytes

#security #cve #cybersecurity

Traefik's Eternal Wait: Bypassing TCP Timeouts with Postgres Magic Bytes

Vulnerability ID: CVE-2026-25949
CVSS Score: 7.5
Published: 2026-02-12

Traefik, the ubiquitous cloud-native edge router, has a nasty habit of trusting Postgres connections too early. CVE-2026-25949 allows an unauthenticated attacker to bypass configured read timeouts by initiating a Postgres STARTTLS handshake and then simply... stopping. By sending a specific 8-byte sequence, an attacker can trick Traefik into removing its safety deadlines, causing the server to hold the connection open indefinitely. A few thousand of these 'zombie' connections are enough to exhaust file descriptors and goroutines, effectively bricking the load balancer.

TL;DR

A Denial of Service (DoS) vulnerability exists in Traefik versions prior to 3.6.8. By sending a Postgres SSLRequest header (0x0000000804D2162F) and then stalling, an attacker can bypass the readTimeout setting. Traefik indefinitely waits for a TLS ClientHello that never comes, leading to resource exhaustion.

Technical Details

  • CWE ID: CWE-400 (Uncontrolled Resource Consumption)
  • Attack Vector: Network (Remote)
  • CVSS v3.1: 7.5 (High)
  • Impact: Denial of Service (DoS)
  • Affected Protocol: TCP (Postgres STARTTLS)
  • Patch Commit: 31e566e9f1d7888ccb6fbc18bfed427203c35678

Affected Systems

  • Traefik Proxy (Versions < 3.6.8)
  • Traefik: < 3.6.8 (Fixed in: 3.6.8)

Code Analysis

Commit: 31e566e

Fix: postpone setting deadline for postgres starttls

pkg/server/router/tcp/router.go: - if err := conn.SetDeadline(time.Time{}); err != nil { ... }
Enter fullscreen mode Exit fullscreen mode

Exploit Details

  • Internal Research: The vulnerability is trivial to exploit using standard socket libraries by sending the Postgres SSLRequest prelude and pausing.

Mitigation Strategies

  • Upgrade to Traefik v3.6.8 or later immediately.
  • Implement connection.maxLessHost to limit connections per IP.
  • Configure strict idle timeouts on upstream load balancers (AWS ALB/NLB, Cloudflare).

Remediation Steps:

  1. Pull the latest Traefik image: docker pull traefik:v3.6.8.
  2. Update your docker-compose.yml or Kubernetes manifests to use the new tag.
  3. Redeploy the Traefik ingress controller.
  4. Verify the fix by attempting the PoC script against a staging environment.

References

Read the full report for CVE-2026-25949 on our website for more details including interactive diagrams and full exploit analysis.

Top comments (0)