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OpenAdvisories
Medium · 5.9 CVE-2025-66491 EUVD-2025-201730GHSA-7vww-mvcr-x6vjGO-2025-4205

Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider

Published Dec 9, 2025 · Updated Dec 9, 2025 · Assigned by GitHub_M

Description

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.

Affected products

VendorProductAffectedFixed
traefik traefik >= 3.5.0, < 3.6.3 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
openSUSE Tumbleweed traefik 3.6.6-1.1 openSUSE-SU-2026:10020-1
openSUSE Leap 16.0 govulncheck-vulndb 0.0.20260723T184607-160000.1.1 openSUSE-SU-2026:21483-1
openSUSE Leap 15.6 govulncheck-vulndb 0.0.20251230T014957-150000.1.134.1 SUSE-SU-2026:0037-1

Affected packages

EcosystemPackageAffectedFixedRecord
Go github.com/traefik/traefik all versions — GO-2025-4205
Go github.com/traefik/traefik/v2 all versions — GO-2025-4205
Go github.com/traefik/traefik/v3 >= 3.5.0, < 3.6.3 3.6.3 GHSA-7vww-mvcr-x6vj

Advisories 3

References