What’s Vulnerable › Vulnerabilities

CVE-2026-56743: Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-15 · updated 2026-07-17
• Weakness: CWE-863

Description

Cilium is a networking, observability, and security solution. From 1.19.0 to 1.19.4, standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule when Cilium is configured with a custom clusterName rather than the default any value. The parser incorrectly instantiates a pod selector on selectorless peer definitions, allowing traffic from other workloads in the same namespace as the subject of the policy. This issue is fixed in version 1.19.5.

Affected products

• cilium: from 1.19.0 before 1.19.5 — fixed in 1.19.5

How to fix

Upgrade to a fixed version: cilium 1.19.5. Check the vendor advisory for mitigations.

References

• https://github.com/cilium/cilium/commit/1c84ae3b58a7cd54f7ee355e6c524c82f620eae8
• https://github.com/cilium/cilium/commit/bacea640404c0805c23515353dc1681c5bf35171
• https://github.com/cilium/cilium/pull/46305
• https://github.com/cilium/cilium/pull/46456
• https://github.com/cilium/cilium/releases/tag/v1.19.5
• https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r

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