PatchSiren cyber security CVE debrief
CVE-2026-56743 cilium CVE debrief
A medium-severity vulnerability was found in Cilium, a networking, observability, and security solution. The issue arises from incorrect handling of standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors when Cilium is configured with a custom clusterName. This results in the erroneous generation of a wildcard namespace allow rule, allowing traffic from other workloads in the same namespace as the subject of the policy. The vulnerability is fixed in version 1.19.5.
- Vendor
- cilium
- Product
- Unknown
- CVSS
- MEDIUM 5.4
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-15
- Original CVE updated
- 2026-07-16
- Advisory published
- 2026-07-15
- Advisory updated
- 2026-07-16
Who should care
Users of Cilium, particularly those who have configured it with a custom clusterName and are using versions between 1.19.0 and 1.19.4, should be aware of this vulnerability and take steps to mitigate it.
Technical summary
Cilium, a networking, observability, and security solution, is vulnerable to a medium-severity issue. The problem occurs when using standard Kubernetes NetworkPolicy specifications with CIDR-based ipBlock rules lacking pod or namespace selectors, and Cilium is set up with a custom clusterName. This misconfiguration leads to the incorrect creation of a wildcard namespace allow rule, permitting traffic from other workloads within the same namespace as the policy's subject. The issue is resolved in Cilium version 1.19.5.
Defensive priority
Medium
Recommended defensive actions
- Upgrade to Cilium version 1.19.5 or later
- Review and update existing NetworkPolicy specifications to ensure they do not rely on CIDR-based ipBlock rules without pod or namespace selectors
- Monitor network traffic and workload communications to detect potential exploitation attempts
- Perform a thorough review of the network topology to identify potential exposure
- Verify that compensating controls are in place for exposed systems
- Conduct regular asset inventory to ensure all deployments are accounted for
- Track and document changes to the environment until remediation is verified
Evidence notes
The CVE record was published on 2026-07-15T20:17:51.987Z and was last modified on 2026-07-16T14:16:55.410Z. The NVD entry is currently Undergoing Analysis. The vulnerability has a CVSS score of 5.4 and a severity of MEDIUM.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-15T20:17:51.987Z and has not been modified since then. The NVD entry is currently Undergoing Analysis.