Bug 2444876 (CVE-2026-26998)

Summary: CVE-2026-26998 github.com/traefik/traefik: Traefik: Denial of Service due to unbounded ForwardAuth middleware response processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
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. When Traefik is configured to use the ForwardAuth middleware, it reads the authentication server's response body into memory without a size limit. A malicious or misconfigured authentication server could send an excessively large response, causing Traefik to consume all available memory. This leads to an out-of-memory (OOM) condition, crashing the Traefik process and resulting in a denial of service for all routes it manages.
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Description OSIDB Bzimport 2026-03-05 19:01:39 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 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.