CVE-2025-66491
published 2025-12-09CVE-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…
PriorityP430medium5.9CVSS 3.1
AVNACHPRNUINSUCHINAN
EPSS
0.21%
10.6th percentile
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
3 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| github.com | traefik_traefik_v3 | >= 3.5.0 < 3.6.3 | 3.6.3 |
| traefik | traefik | — | — |
| traefik | traefik | >= 3.5.0 < 3.6.3 | 3.6.3 |
CVSS provenance
nvdv3.15.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
vendor_redhat5.9MEDIUM
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OSV
Traefik Inverted TLS Verification Logic in ingress-nginx Provider in github.com/traefik/traefik
osv·2025-12-15
CVE-2025-66491 Traefik Inverted TLS Verification Logic in ingress-nginx Provider in github.com/traefik/traefik
Traefik Inverted TLS Verification Logic in ingress-nginx Provider in github.com/traefik/traefik
Traefik Inverted TLS Verification Logic in ingress-nginx Provider in github.com/traefik/traefik
OSV
Traefik Inverted TLS Verification Logic in ingress-nginx Provider
osv·2025-12-08
CVE-2025-66491 [MEDIUM] Traefik Inverted TLS Verification Logic in ingress-nginx Provider
Traefik Inverted TLS Verification Logic in ingress-nginx Provider
## Impact
There is a potential vulnerability in 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.
## Patches
- https://github.com/traefik/traefik/releases/tag/v3.6.3
## For more information
If you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).
Original Description
### Summary
A l
GHSA
Traefik Inverted TLS Verification Logic in ingress-nginx Provider
ghsa·2025-12-08
CVE-2025-66491 [MEDIUM] CWE-295 Traefik Inverted TLS Verification Logic in ingress-nginx Provider
Traefik Inverted TLS Verification Logic in ingress-nginx Provider
## Impact
There is a potential vulnerability in 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.
## Patches
- https://github.com/traefik/traefik/releases/tag/v3.6.3
## For more information
If you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).
Original Description
### Summary
A l
Red Hat
github.com/traefik/traefik: Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider
vendor_redhat·2025-12-09·CVSS 5.9
CVE-2025-66491 [MEDIUM] CWE-295 github.com/traefik/traefik: Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider
github.com/traefik/traefik: Traefik has Inverted TLS Verification Logic in its ingress-nginx Provider
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.
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
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2025-12-09
Published