ISTIO-SECURITY-2021-006
An external client can access unexpected services in the cluster, bypassing authorization checks, when a gateway is configured with `AUTO_PASSTHROUGH` routing configuration.
| Disclosure Details | |
|---|---|
| CVE(s) | CVE-2021-31921 |
| CVSS Impact Score | 10 AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| Affected Releases | All releases prior to 1.8.6 1.9.0 to 1.9.4 |
Issue
Istio contains a remotely exploitable vulnerability where an external client can access unexpected services in the cluster,
bypassing authorization checks, when a gateway is configured with AUTO_PASSTHROUGH routing configuration.
Am I impacted?
This vulnerability impacts only usage of the AUTO_PASSTHROUGH Gateway type, which is typically only used in multi-network multi-cluster deployments.
The TLS mode of all Gateways in the cluster can be detected with the following command:
$ kubectl get gateways.networking.istio.io -A -o "custom-columns=NAMESPACE:.metadata.namespace,NAME:.metadata.name,TLS_MODE:.spec.servers[*].tls.mode"
If the output shows any AUTO_PASSTHROUGH Gateways, you may be impacted.
Mitigation
Update your cluster to the latest supported version:
- Istio 1.8.6, if using 1.8.x
- Istio 1.9.5 or up
- The patch version specified by your cloud provider
Credit
We would like to thank John Howard (Google) for reporting this issue.