CIDR deny policies may not take effect when a more narrow CIDR allow is present

Summary

Cilium is a networking, observability, and security solution with an eBPF-based dataplane. Starting in version 1.14.0 and prior to versions 1.14.16 and 1.15.10, 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`.This issue has been patched in Cilium v1.14.16 and v1.15.10. As this issue only affects policies using `enableDefaultDeny: false` or that set `toEntities` to `all`, some workarounds are available. For users with policies using `enableDefaultDeny: false`, remove this configuration option and explicitly define any allow rules required. For users with egress policies that explicitly specify `toEntities: all`, use `toEntities: world`.

Timeline

1. Oct 21, 2024, 7:05 PM UTCCVE published
2. Oct 21, 2024, 7:58 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Oct 21, 2024, 7:59 PM UTCRecord last updated

Affected versions

• cilium cilium

  From 1.15.0 · fixed in 1.15.10; From 1.14.0 · fixed in 1.14.16

• github.com/cilium/ciliumGo

  From 1.14.0 · fixed in 1.14.16; From 1.15.0 · fixed in 1.15.10

• github.com/cilium/ciliumGo

  From 1.15.0 · fixed in 1.15.10

• github.com/cilium/ciliumGo

  From 1.14.0 · fixed in 1.14.16

References 1