Bug 2444874 (CVE-2026-26999)

Summary: CVE-2026-26999 github.com/traefik/traefik: Traefik: Denial of Service due to incomplete TLS handshake
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Traefik, an HTTP reverse proxy and load balancer. A remote unauthenticated client can exploit this vulnerability by sending an incomplete Transport Layer Security (TLS) record, which causes the TLS handshake to stall indefinitely. This can lead to resource exhaustion, such as file descriptors and goroutines, ultimately degrading the availability of all services on the affected entrypoint, resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-03-05 19:01:33 UTC 
Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. This issue has been patched in versions 2.11.38 and 3.6.9.