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