PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-56742 cilium CVE debrief

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. This issue has a medium CVSS score of 5.9 and is fixed in Cilium versions 1.17.17, 1.18.11, and 1.19.5. Gateway API functionality is disabled by default.

Vendor
cilium
Product
Unknown
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-15
Original CVE updated
2026-07-17
Advisory published
2026-07-15
Advisory updated
2026-07-17

Who should care

Users of Cilium clusters with Gateway API enabled, particularly those with permissions to create or update namespaced HTTPRoutes, should review their configurations and ensure that proper authorization mechanisms are in place.

Technical summary

Prior to Cilium versions 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. This issue has a medium CVSS score of 5.9. Gateway API functionality is disabled by default. Users should review and restrict permissions for creating or updating namespaced HTTPRoutes.

Defensive priority

Medium priority due to the medium CVSS score of 5.9 and the potential for traffic mirroring across namespaces.

Recommended defensive actions

  • Update Cilium to version 1.17.17, 1.18.11, or 1.19.5
  • Review and restrict permissions for creating or updating namespaced HTTPRoutes
  • Monitor traffic and audit logs for potential exploitation attempts
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-15T20:17:51.850Z and was last modified on 2026-07-16T14:16:55.273Z. The NVD entry is currently Undergoing Analysis. This information is based on the CVE record and NVD entry. Further verification is recommended.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-56742 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-56742

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-56742 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-56742

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.