Answer in brief
CVE-2026-56742 records a Medium severity (CVSS 5.9) vulnerability in Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces. The current sources do not mark it as known exploited. The current feed maps github.com/cilium/cilium (go), github.com/cilium/cilium (go), github.com/cilium/cilium (go), github.com/cilium/cilium (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps github.com/cilium/cilium (go), github.com/cilium/cilium (go), github.com/cilium/cilium (go), github.com/cilium/cilium (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/cilium/ciliumgo | <1.17.17 | 1.17.17 |
| github.com/cilium/ciliumgo | >=1.19.0,<1.19.5 | 1.19.5 |
| github.com/cilium/ciliumgo | >=0 <1.17.17 | 1.17.17 |
| github.com/cilium/ciliumgo | >=1.19.0 <1.19.5 | 1.19.5 |
| github.com/cilium/ciliumCiliumgo | >=1.18.0,<1.18.11 | 1.18.11 |
| github.com/cilium/ciliumCiliumgo | >=1.18.0 <1.18.11 | 1.18.11 |
Published upstream
Jul 15, 2026
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Sep 24, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Jul 15, 2026
### 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 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](https://docs.cilium.io/en/latest/community/community/). 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]](mailto:[email protected]). This is a private mailing list for the Cilium security team, and your report will be treated as top priority.
Quoted source text, attributed separately from HOL analysis.