CVE-2026-22045
Published: 15 January 2026
Summary
CVE-2026-22045 is a medium-severity Allocation of Resources Without Limits or Throttling (CWE-770) vulnerability in Traefik Traefik. Its CVSS base score is 5.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application Exhaustion Flood (T1499.003); ranked at the 6.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SC-6 (Resource Availability).
Deeper analysis
CVE-2026-22045 is a denial-of-service vulnerability in Traefik, an open-source HTTP reverse proxy and load balancer. It affects versions prior to 2.11.35 and 3.6.7, specifically in the ACME TLS certificates' automatic generation feature when the ACME TLS challenge is enabled. The issue stems from the ACME TLS-ALPN fast path, which allows unauthenticated clients to indefinitely tie up Go routines and file descriptors. This is classified under CWE-770 (Allocation of Resources Without Limits or Throttling) with a CVSS v3.1 base score of 5.9 (AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H).
Any unauthenticated attacker with network access to the Traefik entry point can exploit this vulnerability. The attack involves opening numerous TCP connections, sending a minimal TLS ClientHello containing the acme-tls/1 ALPN identifier, and then ceasing to respond. This exhausts server resources, leading to denial of service on the affected entry point by preventing legitimate traffic from being processed.
Traefik addresses the vulnerability in releases 2.11.35 and 3.6.7, as detailed in the project's security advisory (GHSA-cwjm-3f7h-9hwq) and corresponding release notes. The fixing commit (e9f3089e9045812bcf1b410a9d40568917b26c3d) resolves the resource exhaustion in the ACME TLS-ALPN handling. Security practitioners should upgrade to these patched versions and review configurations to ensure ACME TLS challenges are only enabled where necessary.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2949
Vulnerability details
Traefik is an HTTP reverse proxy and load balancer. Prior to 2.11.35 and 3.6.7, there is a potential vulnerability in Traefik ACME TLS certificates' automatic generation: the ACME TLS-ALPN fast path can allow unauthenticated clients to tie up go routines…
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and file descriptors indefinitely when the ACME TLS challenge is enabled. A malicious client can open many connections, send a minimal ClientHello with acme-tls/1, then stop responding, leading to denial of service of the entry point. The vulnerability is fixed in 2.11.35 and 3.6.7.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct resource exhaustion DoS via unauthenticated TLS-ALPN connections targeting application-layer handling in a public-facing proxy.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires protections against resource-exhaustion DoS on network entry points, exactly matching the ACME TLS-ALPN fast-path attack that ties up goroutines and file descriptors.
Mandates controls that ensure resource availability by limiting allocation of connections, threads, and descriptors, preventing indefinite consumption by unauthenticated acme-tls/1 clients.
Limits the number of concurrent sessions or connections per client or entry point, mitigating the ability of a single unauthenticated attacker to open many TLS-ALPN connections.