Headline
GHSA-j777-63hf-hx76: Envoy Admin Interface Exposed through prometheus metrics endpoint
Impact
A user with access to a Kubernetes cluster where Envoy Gateway is installed can use a path traversal attack to execute Envoy Admin interface commands on proxies managed by Envoy Gateway. The admin interface can be used to terminate the Envoy process and extract the Envoy configuration (possibly containing confidential data).
For example, the following command, if run from within the Kubernetes cluster, can be used to get the configuration dump of the proxy:
curl --path-as-is http://<Proxy-Service-ClusterIP>:19001/stats/prometheus/../../config_dump
Patches
1.2.6
Workarounds
The EnvoyProxy API can be used to apply a bootstrap config patch that restricts access strictly to the prometheus stats endpoint. Find below an example of such a bootstrap patch.
apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyProxy
metadata:
name: custom-proxy-config
namespace: default
spec:
bootstrap:
type: JSONPatch
jsonPatches:
- op: "add"
path: "/static_resources/listeners/0/filter_chains/0/filters/0/typed_config/normalize_path"
value: true
- op: "replace"
path: "/static_resources/listeners/0/filter_chains/0/filters/0/typed_config/route_config/virtual_hosts/0/routes/0/match"
value:
path: "/stats/prometheus"
headers:
- name: ":method"
exact_match: GET
References
- Envoy Admin Interface: https://www.envoyproxy.io/docs/envoy/latest/operations/admin
- Envoy Configuration Best Practices: https://www.envoyproxy.io/docs/envoy/latest/configuration/best_practices/edge
Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.