Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces

HIGH 8.9CVE-2026-56742 · BIT-cilium-2026-56742 · BIT-cilium-operator-2026-56742 · Published 15/07/2026 · updated 17/07/2026

In short

CVE-2026-56742 is a HIGH (CVSS 8.9) vulnerability affecting github.com/cilium/cilium, github.com/cilium/ciliumCilium, cilium (cilium).
Chance of exploitation in the next 30 days (EPSS): 0.18%, higher than 7.0% of all vulnerabilities.
Fix: update to 1.18.11, 1.19.5, 1.17.17 or later.

Package	Affected versions	Patched versions
github.com/cilium/cilium Go	`≥ 1.18.0, < 1.18.11≥ 1.19.0, < 1.19.5< 1.17.17`	`1.18.111.19.51.17.17`
github.com/cilium/ciliumCilium Go	`≥ 1.18.0, < 1.18.11`	`1.18.11`
cilium cilium	`≥ 1.18.0, < 1.18.11≥ 1.19.0, < 1.19.5< 1.17.17`	`1.18.111.19.51.17.17`

Description

Impact

In Cilium clusters using 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 versions of Cilium before v1.17.17

This issue is patched in:

Cilium v1.19.5
Cilium v1.18.11
Cilium v1.17.17

Workarounds

There is no workaround to this issue. Users of this feature who are unable to upgrade can mitigate the risk by ensuring that RBAC permissions to create HTTPRoute objects are only granted to cluster admins.

Acknowledgements

The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @galanko for reporting the issue and @mhofstetter for their work on triaging and remediating this issue.

For more information

If you have any questions or comments about this advisory, please reach out on Slack.

If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.

NVD description

Cilium is a networking, observability, and security solution. Prior to 1.17.17, 1.18.11, and 1.19.5, Cilium clusters using Gateway API allow users with permissions to create or update namespaced HTTPRoutes to mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism. Gateway API functionality is disabled by default. This issue is fixed in versions 1.17.17, 1.18.11, and 1.19.5.