CVE-2026-26998: Traefik: unbounded io.ReadAll on auth server response body causes OOM denial of service(DOS)

Vulnerability summary

CVE-2026-26998 is a medium (CVSS 4.4) vulnerability in traefik. EPSS estimates a 0.51% chance of exploitation in the next 30 days, higher than 43.4% of scored vulnerabilities.

Timeline

1. 05-03-2026
   PublishedVulnerability first disclosed.
2. 06-03-2026
   Last modifiedVulnerability information updated.

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 the ForwardAuth middleware responses. When Traefik is configured to use the ForwardAuth middleware, the response body from the authentication server is read entirely into memory without any size limit. There is no maxResponseBodySize configuration to restrict the amount of data read from the authentication server response. If the authentication server returns an unexpectedly large or unbounded response body, Traefik will allocate unlimited memory, potentially causing an out-of-memory (OOM) condition that crashes the process. This results in a denial of service for all routes served by the affected Traefik instance. This issue has been patched in versions 2.11.38 and 3.6.9.

• CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.