CVE-2026-22771: Envoy Gateway Information Disclosure Flaw

CVE-2026-22771 Overview

CVE-2026-22771 is a Code Injection vulnerability affecting Envoy Gateway, an open source project for managing Envoy Proxy as a standalone or Kubernetes-based application gateway. Prior to versions 1.5.7 and 1.6.2, EnvoyExtensionPolicy Lua scripts executed by Envoy proxy can be exploited to leak the proxy's credentials. These compromised credentials can subsequently be used to communicate with the control plane and gain unauthorized access to all secrets used by Envoy proxy, including TLS private keys and credentials used for downstream and upstream communication.

Critical Impact

Attackers exploiting this vulnerability can exfiltrate proxy credentials via malicious Lua scripts, potentially gaining access to TLS private keys and all secrets managed by Envoy Gateway, leading to complete compromise of encrypted communications and service authentication.

Affected Products

• Envoy Gateway versions prior to 1.5.7
• Envoy Gateway versions prior to 1.6.2
• Kubernetes deployments utilizing EnvoyExtensionPolicy with Lua scripts

Discovery Timeline

• 2026-01-12 - CVE CVE-2026-22771 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2026-22771

Vulnerability Analysis

This vulnerability stems from CWE-94 (Improper Control of Generation of Code), commonly known as Code Injection. The EnvoyExtensionPolicy feature in Envoy Gateway allows administrators to define custom Lua scripts that are executed within the Envoy proxy context. However, these Lua scripts have access to sensitive runtime information, including the proxy's credentials used for control plane communication.

When a malicious or improperly secured Lua script is executed, it can access and exfiltrate these credentials. Once obtained, an attacker can impersonate the Envoy proxy to the control plane, effectively gaining access to all secrets that the proxy is authorized to retrieve. This includes TLS private keys used for encrypting traffic and credentials used for authenticating to upstream and downstream services.

The vulnerability is particularly dangerous in multi-tenant Kubernetes environments where EnvoyExtensionPolicy configurations may be less strictly controlled, or where Lua script content is derived from user-provided or less-trusted sources.

Root Cause

The root cause of CVE-2026-22771 is insufficient isolation and access control for Lua scripts executed within the Envoy proxy runtime environment. The Lua scripting context has implicit access to internal proxy credentials and secrets without adequate sandboxing or permission boundaries. This design allows any code running in the Lua context to access sensitive authentication material that should be protected from arbitrary script execution.

Attack Vector

The attack vector is network-based and requires low privileges to exploit. An attacker who can influence or inject EnvoyExtensionPolicy Lua scripts within the Envoy Gateway configuration can craft malicious code that:

1. Accesses the proxy's internal credential storage during script execution
2. Exfiltrates these credentials to an attacker-controlled endpoint
3. Uses the stolen credentials to establish unauthorized communication with the Envoy Gateway control plane
4. Retrieves all secrets accessible to the proxy, including TLS private keys and authentication credentials

The vulnerability mechanism involves Lua scripts having unrestricted access to the proxy's runtime context. When such scripts execute, they can enumerate and extract credential material through the Lua environment. For detailed technical information on the exploitation mechanics, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-22771

Indicators of Compromise

• Unusual outbound network connections from Envoy proxy containers to unexpected external endpoints
• Unauthorized API calls to the Envoy Gateway control plane from unexpected sources
• Anomalous access patterns to secrets or TLS certificates in the Kubernetes secrets store
• Unexpected modifications to EnvoyExtensionPolicy resources in the cluster

Detection Strategies

• Monitor and audit all EnvoyExtensionPolicy Lua script configurations for unauthorized changes or suspicious code patterns
• Implement network traffic analysis to detect credential exfiltration attempts from proxy pods
• Enable verbose logging for Envoy Gateway control plane to identify unauthorized secret access requests
• Deploy runtime security monitoring within Envoy proxy containers to detect suspicious Lua script behavior

Monitoring Recommendations

• Configure SentinelOne Singularity Platform to monitor Kubernetes workloads for anomalous process behavior in Envoy containers
• Establish baseline network behavior for Envoy proxy pods and alert on deviations indicating potential credential exfiltration
• Implement audit logging for all EnvoyExtensionPolicy create, update, and delete operations in Kubernetes
• Monitor control plane authentication logs for connections from unexpected client certificates or credentials

How to Mitigate CVE-2026-22771

Immediate Actions Required

• Upgrade Envoy Gateway to version 1.5.7 or 1.6.2 immediately to address this vulnerability
• Audit all existing EnvoyExtensionPolicy configurations for Lua scripts that may have been compromised
• Review and rotate all secrets accessible by Envoy proxy, including TLS private keys and authentication credentials
• Implement strict RBAC policies to limit who can create or modify EnvoyExtensionPolicy resources

Patch Information

The vulnerability has been addressed in Envoy Gateway versions 1.5.7 and 1.6.2. Organizations should upgrade to these patched versions as the primary remediation approach. The fix implements proper isolation and access controls for Lua scripts, preventing unauthorized access to proxy credentials. For complete patch details, refer to the GitHub Security Advisory.

Workarounds

• Disable EnvoyExtensionPolicy Lua script functionality if not required for operations until patching is complete
• Implement network policies to restrict outbound connections from Envoy proxy pods to only required destinations
• Apply Kubernetes admission controllers to validate and restrict EnvoyExtensionPolicy configurations
• Segment control plane access using network policies to limit potential lateral movement if credentials are compromised

# Example: Restrict EnvoyExtensionPolicy creation to specific namespaces
kubectl create rolebinding envoy-policy-admin \
  --clusterrole=envoy-gateway-policy-admin \
  --user=trusted-admin \
  --namespace=envoy-gateway-system

# Example: Network policy to restrict Envoy proxy egress
kubectl apply -f - <<EOF
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: restrict-envoy-egress
  namespace: envoy-gateway-system
spec:
  podSelector:
    matchLabels:
      app: envoy
  policyTypes:
  - Egress
  egress:
  - to:
    - namespaceSelector:
        matchLabels:
          kubernetes.io/metadata.name: envoy-gateway-system
EOF