CVE-2026-28459: OpenClaw Path Traversal Vulnerability

CVE-2026-28459 Overview

OpenClaw versions prior to 2026.2.12 contain a path traversal vulnerability that allows authenticated gateway clients to write transcript data to arbitrary locations on the host filesystem. The application fails to validate the sessionFile path parameter, enabling attackers to supply a path outside the intended sessions directory. This can result in the creation of arbitrary files and repeated data appending, potentially leading to configuration corruption or denial of service.

Critical Impact

Authenticated attackers can exploit this arbitrary file write vulnerability to corrupt critical configuration files, overwrite system data, or cause denial of service through disk exhaustion on affected OpenClaw installations.

Affected Products

• OpenClaw versions prior to 2026.2.12

Discovery Timeline

• 2026-03-05 - CVE-2026-28459 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-28459

Vulnerability Analysis

This vulnerability is classified as CWE-73 (External Control of File Name or Path), a path traversal weakness that occurs when software uses external input to construct a pathname without properly neutralizing special elements. In OpenClaw, the sessionFile parameter accepts user-controlled input from authenticated gateway clients without adequate validation or sanitization.

When a gateway client initiates a session, the application uses the provided sessionFile path to determine where transcript data should be written. Because the path is not restricted to a designated sessions directory, an attacker can craft a malicious path using directory traversal sequences (such as ../) to escape the intended directory and target arbitrary filesystem locations accessible by the OpenClaw process.

The vulnerability requires authentication, meaning only users with valid gateway credentials can exploit this flaw. However, once authenticated, the attacker gains the ability to write to any file writable by the OpenClaw service account. Since transcript data is appended repeatedly during session activity, this can be weaponized for various attack scenarios including configuration file corruption and denial of service through disk space exhaustion.

Root Cause

The root cause of this vulnerability is insufficient input validation on the sessionFile path parameter. The application fails to implement proper path canonicalization and boundary checks before using the user-supplied path for file operations. Without validation to ensure the resolved path remains within the expected sessions directory, directory traversal sequences in the input can redirect file writes to unintended locations.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access to the OpenClaw gateway interface. The exploitation flow involves:

1. An attacker authenticates to the OpenClaw gateway with valid credentials
2. During session initialization, the attacker provides a malicious sessionFile parameter containing path traversal sequences
3. The application constructs the file path without validating that it resolves to a location within the sessions directory
4. Transcript data is written to the attacker-specified location
5. Subsequent session activity appends additional data to the target file

This can be leveraged to corrupt configuration files by appending garbage data, overwrite logs to cover tracks, or fill disk space to cause denial of service. For detailed technical implementation, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-28459

Indicators of Compromise

• Unexpected files appearing outside the OpenClaw sessions directory with transcript-like content
• Unusual file modification timestamps on configuration files or system files writable by the OpenClaw service
• Session logs showing sessionFile parameters containing path traversal sequences such as ../ or absolute paths
• Rapid disk usage growth in non-session directories attributed to the OpenClaw process

Detection Strategies

• Implement file integrity monitoring (FIM) on critical configuration files and directories outside the sessions path
• Monitor OpenClaw process file write operations for paths outside the expected sessions directory
• Create alerting rules for sessionFile parameter values containing directory traversal patterns in gateway request logs
• Deploy application-layer logging to capture and analyze all session initialization requests

Monitoring Recommendations

• Enable verbose logging for OpenClaw gateway operations to capture full request parameters
• Configure SIEM rules to detect anomalous file write patterns from the OpenClaw service account
• Establish baseline metrics for session directory file counts and sizes to detect deviation
• Monitor for signs of disk exhaustion attacks such as sudden increases in write activity or disk utilization

How to Mitigate CVE-2026-28459

Immediate Actions Required

• Upgrade OpenClaw to version 2026.2.12 or later immediately
• Audit recent session logs for suspicious sessionFile values containing path traversal sequences
• Review filesystem for unauthorized files that may have been created through exploitation
• Restrict network access to the OpenClaw gateway to trusted clients only until patching is complete

Patch Information

The OpenClaw maintainers have addressed this vulnerability in version 2026.2.12. The fix implements proper path validation to ensure the sessionFile parameter cannot reference locations outside the designated sessions directory. Security patches are available via the following commits:

• First patch commit
• Second patch commit

Organizations should review the GitHub Security Advisory and VulnCheck Advisory for complete details.

Workarounds

• Deploy a web application firewall (WAF) rule to block gateway requests containing path traversal sequences in the sessionFile parameter
• Run the OpenClaw service under a restricted user account with minimal filesystem write permissions
• Use filesystem sandboxing or container isolation to limit the directories writable by the OpenClaw process
• Implement network segmentation to restrict which clients can reach the gateway interface

# Example: Restrict OpenClaw service permissions
# Create dedicated user with limited write access
useradd -r -s /sbin/nologin openclaw-svc
chown -R openclaw-svc:openclaw-svc /var/lib/openclaw/sessions
chmod 750 /var/lib/openclaw/sessions

# Remove write permissions from other directories
# Ensure service runs as restricted user in systemd unit
# [Service]
# User=openclaw-svc
# ReadWritePaths=/var/lib/openclaw/sessions
# ProtectSystem=strict