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GHSA-fm8w-2m5w-9j7r
github.com/cilium/ciliumImpact
Standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule under specific cluster configurations.
When Cilium deployment is configured with a specific custom clusterName (rather than the default "any" value), the parser incorrectly instantiates a pod selector on selectorless peer definitions. This leads to Cilium appending an unintended wildcard namespace label selector to the policy's allowed Layer 3 rules, which allows traffic from other workloads in the same namespace as the subject of the policy.
Example policy affected by this issue:
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: test-server
namespace: default
spec:
podSelector:
matchLabels:
app: test-server
policyTypes:
- Ingress
ingress:
- from:
- ipBlock:
cidr: 192.0.2.3
In affected versions, this policy erroneously allows the test-server Pod in the default namespace to receive any traffic from other workloads running in the default namespace.
Patches
This issue has been patched in:
- Cilium v1.19.5
Releases below v1.19.0 are not affected.
This issue affects:
- Cilium v1.19 between v1.19.0 and v1.19.4 inclusive
Workarounds
Developers can create the equivalent policy using CiliumNetworkPolicy fromCIDR expressions. CiliumNetworkPolicy and CiliumClusterwideNetworkPolicy are not affected by this issue.
Acknowledgements
Special thanks to @TheBeeZee for reporting this issue and preparing the fix, and to @fristonio and @odinuge for their assistance in reviewing the solution.
For more information
If a vulnerability affecting Cilium appears to have been found, the Cilium security team strongly encourages reporting it to the security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and the report will be treated as top priority.
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The vulnerability can be exploited over a local network, such as Wi-Fi. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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