CVE-2026-42427: OpenClaw RCE Vulnerability

CVE-2026-42427 Overview

OpenClaw before version 2026.4.8 contains a remote code execution vulnerability caused by missing environment variable denylist entries. The vulnerability allows attackers to inject malicious build tool environment variables including HGRCPATH, CARGO_BUILD_RUSTC_WRAPPER, RUSTC_WRAPPER, and MAKEFLAGS to influence host exec commands and achieve arbitrary code execution.

Critical Impact
Attackers can leverage unfiltered environment variables to inject malicious payloads into build processes, enabling arbitrary code execution on systems running vulnerable OpenClaw versions.

Affected Products

OpenClaw versions prior to 2026.4.8
OpenClaw for Node.js (all vulnerable versions)

Discovery Timeline

2026-04-28 - CVE-2026-42427 published to NVD
2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-42427

Vulnerability Analysis

This vulnerability stems from an incomplete input validation mechanism (CWE-184: Incomplete List of Disallowed Inputs) in OpenClaw's environment variable handling. The application maintains a denylist of potentially dangerous environment variables to prevent injection attacks, but fails to include critical build tool variables that can be weaponized for code execution.

The missing denylist entries include variables that control build tool behavior: HGRCPATH (Mercurial configuration path), CARGO_BUILD_RUSTC_WRAPPER and RUSTC_WRAPPER (Rust compiler wrapper paths), and MAKEFLAGS (Make build flags). When these variables are controllable by an attacker, they can redirect build tool execution to malicious binaries or inject arbitrary commands into build processes.

Root Cause

The root cause is an incomplete denylist implementation in the environment variable filtering logic. While OpenClaw implemented protections against common injection vectors, the security team did not account for build tool-specific environment variables that can influence command execution paths. This represents a classic case of CWE-184 where the list of disallowed inputs is insufficient to prevent exploitation.

Attack Vector

The attack requires local access with low privileges. An attacker with the ability to set environment variables can inject malicious values for the unprotected build tool variables. When OpenClaw executes build-related operations, these environment variables influence the behavior of underlying tools, potentially redirecting execution to attacker-controlled code.

The attack flow involves:

Setting malicious environment variables (e.g., RUSTC_WRAPPER=/path/to/malicious/binary)
Triggering an OpenClaw operation that invokes build tools
The build tools honor the injected environment variables, executing attacker-controlled code

typescript

     try {
       assertExplicitProxySupportsPinnedDns(parsedUrl, params.dispatcherPolicy, params.pinDns);
       await assertExplicitProxyAllowed(params.dispatcherPolicy, params.lookupFn, params.policy);
-      const pinned = await resolvePinnedHostnameWithPolicy(parsedUrl.hostname, {
-        lookupFn: params.lookupFn,
-        policy: params.policy,
-      });
       const canUseTrustedEnvProxy =
         mode === GUARDED_FETCH_MODE.TRUSTED_ENV_PROXY && hasProxyEnvConfigured();
       if (canUseTrustedEnvProxy) {
         dispatcher = createHttp1EnvHttpProxyAgent();
       } else if (params.pinDns === false) {
         dispatcher = createPolicyDispatcherWithoutPinnedDns(params.dispatcherPolicy);
       } else {
+        const pinned = await resolvePinnedHostnameWithPolicy(parsedUrl.hostname, {
+          lookupFn: params.lookupFn,
+          policy: params.policy,
+        });
         dispatcher = createPinnedDispatcher(pinned, params.dispatcherPolicy, params.policy);
       }

Source: GitHub Commit Update

Detection Methods for CVE-2026-42427

Indicators of Compromise

Unexpected values in environment variables HGRCPATH, CARGO_BUILD_RUSTC_WRAPPER, RUSTC_WRAPPER, or MAKEFLAGS pointing to non-standard paths
Process execution from unusual directories during OpenClaw build operations
Child processes spawned by OpenClaw executing unexpected binaries
Unusual file access patterns in build tool configuration directories

Detection Strategies

Monitor environment variable modifications for the affected variables (HGRCPATH, CARGO_BUILD_RUSTC_WRAPPER, RUSTC_WRAPPER, MAKEFLAGS) in processes associated with OpenClaw
Implement process lineage monitoring to detect unexpected child processes spawned during build operations
Deploy file integrity monitoring on build tool binaries and configuration files
Use behavioral analysis to detect anomalous execution patterns during OpenClaw operations

Monitoring Recommendations

Enable detailed logging for all OpenClaw operations, particularly those involving external command execution
Configure SIEM rules to alert on environment variable manipulation attempts targeting build tools
Implement network monitoring for any unexpected outbound connections during build processes
Establish baseline behavior for OpenClaw build operations to identify anomalous activity

How to Mitigate CVE-2026-42427

Immediate Actions Required

Upgrade OpenClaw to version 2026.4.8 or later immediately
Audit current environment variable configurations on systems running OpenClaw
Review process execution logs for signs of past exploitation attempts
Implement additional access controls to restrict who can modify environment variables on affected systems

Patch Information

The OpenClaw development team has released a security patch addressing this vulnerability in version 2026.4.8. The fix expands the environment variable denylist to include the previously unprotected build tool variables. The patch is available via the official OpenClaw repository.

For detailed patch information, refer to the GitHub Commit Update and the GitHub Security Advisory GHSA-7437.

Workarounds

Manually sanitize or unset the affected environment variables (HGRCPATH, CARGO_BUILD_RUSTC_WRAPPER, RUSTC_WRAPPER, MAKEFLAGS) before running OpenClaw
Run OpenClaw in isolated container environments with restricted environment variable access
Implement wrapper scripts that validate environment variables before invoking OpenClaw
Use system-level controls to prevent unauthorized modification of critical environment variables

bash

# Temporary workaround: Unset vulnerable environment variables before running OpenClaw
unset HGRCPATH
unset CARGO_BUILD_RUSTC_WRAPPER
unset RUSTC_WRAPPER
unset MAKEFLAGS
# Run OpenClaw with sanitized environment
openclaw <your-command>