SB2026110948 - Multiple vulnerabilities in Cilium

Description

This security bulletin contains information about 2 vulnerabilities.

1) Incorrect authorization (CVE-ID: CVE-2026-56743)

CWE-ID: CWE-863 - Incorrect Authorization

CVSSv4: 5.1 [CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a low-privileged adjacent-network attacker to bypass ingress restrictions and reach protected workloads from within the same namespace.

The vulnerability exists due to Cilium incorrectly adding a wildcard namespace allowance when parsing Kubernetes NetworkPolicy rules containing only an ipBlock match under a non-default clusterName configuration. A low-privileged adjacent-network attacker can send traffic from a workload in the protected workload's namespace, gaining access that the policy should restrict to the specified CIDR.

2) Missing Authorization (CVE-ID: CVE-2026-56742)

CWE-ID: CWE-862 - Missing Authorization

CVSSv4: 4.8 [CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N]

The vulnerability allows a highly privileged adjacent-network attacker to mirror HTTP traffic to any Service in any namespace in a Cilium cluster.

The vulnerability exists due to missing ReferenceGrant authorization checks for cross-namespace HTTPRoute traffic mirroring when Cilium's Gateway API functionality, which is disabled by default, is enabled. A highly privileged adjacent-network attacker can create or update namespaced HTTPRoutes with the required permissions to send mirrored traffic across namespace boundaries without authorization.

Remediation

Install update from vendor's website.

References

• https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r
• https://github.com/cilium/cilium/security/advisories/GHSA-w7c2-w76w-5hmj