Vulnerability Details CVE-2025-66491
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 0.5%
CVSS Severity
CVSS v3 Score 5.9
References
Products affected by CVE-2025-66491
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cpe:2.3:a:traefik:traefik:3.5.0
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cpe:2.3:a:traefik:traefik:3.5.1
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cpe:2.3:a:traefik:traefik:3.5.2
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cpe:2.3:a:traefik:traefik:3.5.3
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cpe:2.3:a:traefik:traefik:3.5.4
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cpe:2.3:a:traefik:traefik:3.5.5
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cpe:2.3:a:traefik:traefik:3.5.6
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cpe:2.3:a:traefik:traefik:3.6.0
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cpe:2.3:a:traefik:traefik:3.6.1
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cpe:2.3:a:traefik:traefik:3.6.2