CVE-2026-25949: Traefik Proxy Denial of Service via STARTTLS Timeout Bypass

CVE-2026-25949 · Severity: high · CVSS 7.5 · Published 2026-02-12

Traefik, a popular cloud-native application proxy, is vulnerable to a denial-of-service attack. An unauthenticated attacker can send a specific 8-byte sequence used by Postgres databases to trick the proxy into keeping a connection open indefinitely. By opening many such connections, an attacker can exhaust the server's resources, causing the proxy to stop responding to legitimate traffic and potentially taking all hosted services offline.

Technologies: github.com/traefik/traefik (Go), github.com/traefik/traefik/v2 (Go), github.com/traefik/traefik/v3 (Go), Traefik, Traefik Labs Traefik Proxy. Vendors: Go, Traefik, Traefik Labs.

Quick answers

Is CVE-2026-25949 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-25949 being exploited in the wild.
How severe is CVE-2026-25949?
High severity, with a CVSS score of 7.5, published 12 February 2026.
Which products and versions are affected?
github.com/traefik/traefik (Go) SEMVER:introduced=0; github.com/traefik/traefik/v2 (Go) SEMVER:introduced=0; github.com/traefik/traefik/v3 (Go) <= 3.6.7, SEMVER:introduced=0,fixed=3.6.8; Traefik Labs Traefik Proxy >= 3.0.0, < 3.6.8.
Is there a fix for CVE-2026-25949?
Yes. github.com/traefik/traefik/v3 (Go): upgrade to 3.6.8 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-25949 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-25949?
Check whether you run github.com/traefik/traefik (Go), github.com/traefik/traefik/v2 (Go), github.com/traefik/traefik/v3 (Go) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/traefik/traefik/v3 (Go): upgrade to 3.6.8 or later
    go get github.com/traefik/traefik/v3@v3.6.8

Technical details

A vulnerability in Traefik's TCP router protocol detection path allows unauthenticated remote attackers to cause a denial of service. When Traefik detects a Postgres SSLRequest (STARTTLS) prelude, it executes a fast-path in 'pkg/server/router/tcp/router.go' that clears all connection deadlines using 'SetDeadline(time.Time{})'. The subsequent Postgres handler then blocks indefinitely while waiting for a TLS ClientHello that never arrives if the attacker stalls. This leads to file-descriptor and goroutine exhaustion. The vulnerability is reachable on any internet-exposed TCP entrypoint during protocol detection, even if no Postgres or TCP routers are explicitly configured. This issue is addressed in version 3.6.8.

Affected products

  • traefik traefik <= 3.6.7

Identifiers

  • CVE-2026-25949
  • GHSA-89p3-4642-cr2w
  • GO-2026-4484

Timeline

  • 2026-02-12: advisory: GitHub Advisory GHSA-89p3-4642-cr2w published
  • 2026-02-12: patched: Fixed in Traefik v3.6.8

References

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