GHSA-3wwx-63fv-pfq6 Cilium's CIDR deny policies may not take effect when a more narrow CIDR allow is present

• Go github.com/cilium/cilium: >= 1.15.0, < 1.15.10 → fixed in 1.15.10 • Go github.com/cilium/cilium: >= 1.14.0, < 1.14.16 → fixed in 1.14.16

Impact A policy rule denying a prefix that is broader than /32 may be ignored if there is • A policy rule referencing a more narrow prefix (`CIDRSet` or `toFQDN`) and • This narrower policy rule specifies either `enableDefaultDeny: false` or `- toEntities: all` Note that a rule specifying `toEntities: world` or `toEntities: 0.0.0.0/0` is insufficient, it must be to entity `all`. As an example, given the below policies, traffic is allowed to 1.1.1.2, when it should be denied: ``` apiVersion: cilium.io/v2 kind: CiliumClusterwideNetworkPolicy metadata: name: block-scary-range spec: endpointSelector: {} egressDeny: • toCIDRSet: • cidr: 1.0.0.0/8 --- apiVersion: cilium.io/v2 kind: CiliumNetworkPolicy metadata: name: evade-deny spec: endpointSelector: {} egress: • toCIDR: • 1.1.1.2/32 • toEntities: • all ``` Patches This issue affects: • Cilium v1.14 between v1.14.0 and v1.14.15 inclusive • Cilium v1.15 between v1.15.0 and v1.15.9 inclusive This issue has been patched in: • Cilium v1.14.16 • Cilium v1.15.10 Workarounds Users with policies using `enableDefaultDeny: false` can work around this issue by removing this configuration option and explicitly defining any allow rules required. No workaround is available to users with egress policies that explicitly specify `toEntities: all`. Acknowledgements The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @squeed, @christarazi, and @jrajahalme for their work in triaging and resolving this issue. For more information If you have any questions or comments about this advisory, please reach out on Slack. If you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at [email protected]. This is a private mailing list for the Cilium security team, and your report will be treated with top priority.