CVE-2026-26999
Published: 05 March 2026
Summary
CVE-2026-26999 is a high-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Traefik Traefik. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 5.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.
Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.
Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.
Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.
Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.
Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.
The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.
Timely maintenance support and spare parts enable rapid recovery from failures induced by uncontrolled resource consumption, shortening the impact window of denial-of-service attacks.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The CVE describes remote exploitation of a TLS handshake resource exhaustion flaw in the public-facing Traefik proxy, directly enabling an application/system exploitation denial-of-service condition via stalled connections.
NVD Description
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…
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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.
Deeper analysisAI
CVE-2026-26999 is a vulnerability in Traefik, an HTTP reverse proxy and load balancer, affecting versions prior to 2.11.38 and 3.6.9. It stems from improper management of TLS handshakes on TCP routers, where the read deadline used for protocol sniffing is cleared before the handshake completes. When a TLS handshake read error occurs, Traefik attempts a second handshake with altered connection parameters while silently ignoring the initial error, as rated at CVSS 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and mapped to CWE-400 (Uncontrolled Resource Consumption).
A remote unauthenticated attacker can exploit this by sending an incomplete TLS record over a TCP router and halting further data transmission. This causes the TLS handshake to stall indefinitely, holding the connection open. By opening many such stalled connections in parallel, the attacker exhausts file descriptors and goroutines, degrading availability of all services on the affected Traefik entrypoint and resulting in a denial-of-service condition.
The vulnerability has been patched in Traefik versions 2.11.38 and 3.6.9. Mitigation involves upgrading to these fixed releases, with details available in the release notes at https://github.com/traefik/traefik/releases/tag/v2.11.38 and https://github.com/traefik/traefik/releases/tag/v3.6.9, as well as the security advisory at https://github.com/traefik/traefik/security/advisories/GHSA-xw98-5q62-jx94.
Details
- CWE(s)