Bug 2420303 (CVE-2025-66491)

Summary: CVE-2025-66491 github.com/traefik/traefik: Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider
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 TLS logic flaw has been discovered in Traefik. The vulnerability exists in the Traefik NGINX provider managing the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. The provider inverts the semantics of the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected.
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Description OSIDB Bzimport 2025-12-09 01:07:11 UTC
Traefik is an HTTP reverse proxy and load balancer. Versions 3.5.0 through 3.6.2 have inverted TLS verification logic in the nginx.ingress.kubernetes.io/proxy-ssl-verify annotation. Setting the annotation to "on" (intending to enable backend TLS certificate verification) actually disables verification, allowing man-in-the-middle attacks against HTTPS backends when operators believe they are protected. This issue is fixed in version 3.6.3.