8.8

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-22771

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

Envoy Gateway is an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway. Prior to 1.5.7 and 1.6.2, EnvoyExtensionPolicy 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. This vulnerability is fixed in 1.5.7 and 1.6.2.

(GitHub Advisory)

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CVE-2026-22771

CVE-2026-22771:

8.8

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/envoyproxy/gateway	go	>= 1.6.0-rc.0, < 1.6.2	1.6.2
github.com/envoyproxy/gateway	go	< 1.5.7	1.5.7

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists because Envoy Gateway's controller validates Lua scripts from EnvoyExtensionPolicy resources by executing them directly, without proper sandboxing. The core of the issue is in the internal/gatewayapi/luavalidator/LuaValidator.runLua function, which, before the patch, would run user-provided Lua code using gopher-lua's DoString method in a default, unrestricted environment. This gave the script access to standard Lua libraries capable of interacting with the underlying operating system, such as io.open and os.execute.

An attacker with permissions to create or edit EnvoyExtensionPolicy resources could submit a script designed to read sensitive files from the controller's filesystem, like the Kubernetes service account token located at /var/run/secrets/kubernetes.io/serviceaccount/token. The script's output or errors, which could contain the stolen token, would then be reflected in the status of the EnvoyExtensionPolicy resource, delivering the credentials to the attacker.

The patch addresses this by implementing a Lua sandbox. A new file, security.lua, is introduced, which explicitly disables dangerous functions (os.execute, io.popen, etc.) and wraps filesystem and environment variable functions (io.open, os.getenv, etc.) to check for access to critical paths and variables. The runLua function was modified to execute this security.lua script before running any user-provided code, effectively creating a sandboxed environment. Additionally, resource limits (execution time, stack size) were added to the Lua state to prevent denial-of-service attacks. The vulnerable function is runLua, and Validate is its public-facing entry point within the validator.

Vulnerable functions

github.com/envoyproxy/gateway/internal/gatewayapi/luavalidator.LuaValidator.runLua

internal/gatewayapi/luavalidator/lua_validator.go

The vulnerability lies in the `runLua` function, which is responsible for executing user-provided Lua scripts for validation purposes within the Envoy Gateway controller. Prior to the patch, this function executed the scripts in an unsandboxed Lua environment. This allowed an attacker to craft a malicious `EnvoyExtensionPolicy` containing Lua code that could use standard libraries like `io` and `os` to read sensitive files (e.g., Kubernetes service account tokens) or execute arbitrary commands on the controller pod. The patch mitigates this by introducing a security sandbox (`security.lua`) that disables or restricts dangerous functions before executing the user's script.

github.com/envoyproxy/gateway/internal/gatewayapi/luavalidator.LuaValidator.Validate

internal/gatewayapi/luavalidator/lua_validator.go

This is the main entry point for validating the Lua script. It orchestrates the validation process and, in the vulnerable version, calls the chain of functions that leads to the unsandboxed execution of the Lua code in `runLua`. An exploit would trigger this function when a malicious `EnvoyExtensionPolicy` is created or updated, making it a key runtime indicator.

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WAF Rule

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Reasoning

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