MEDIUM 5.9 GitHub
CVE-2026-56742
Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces
### Impact
In Cilium clusters using [Gateway API](https://docs.cilium.io/en/stable/network/servicemesh/gateway-api/gateway-api/), users with permissions to create or update namespaced HTTPRoutes can mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism.
Gateway API functionality is disabled by default.
### Patches
This issue affects:
* Cilium v1.19 from v1.19.0 to v1.19.4 inclusive
* Cilium v1.18 from v1.18.0 to v1.18.10 inclusive
* All ve
Affected Products
- go/github.com/cilium/cilium < 1.17.17
- go/github.com/cilium/ciliumCilium >= 1.18.0, < 1.18.11
- go/github.com/cilium/cilium >= 1.19.0, < 1.19.5
References
- https://github.com/advisories/GHSA-w7c2-w76w-5hmj
- https://github.com/cilium/cilium/security/advisories/GHSA-w7c2-w76w-5hmj
- https://nvd.nist.gov/vuln/detail/CVE-2026-56742
- https://github.com/cilium/cilium/commit/7422068aff67ac77c7dcc57aa5b9240c91333deb
This medium severity vulnerability with a CVSS score of 5.9 was published on 2026-09-24 via GitHub. Affected: go/github.com/cilium/cilium < 1.17.17, go/github.com/cilium/ciliumCilium >= 1.18.0, < 1.18.11, go/github.com/cilium/cilium >= 1.19.0, < 1.19.5.
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