CVE-2026-10219: GoClaw RCE Vulnerability via Command Injection

CVE-2026-10219 Overview

CVE-2026-10219 is an operating system command injection vulnerability in nextlevelbuilder GoClaw versions up to 3.11.3. The flaw resides in the FsBridge.WriteFile function within internal/sandbox/fsbridge.go, part of the write_file Tool component. Attackers can manipulate input to this function to inject and execute arbitrary operating system commands. The attack vector is network-based and requires no authentication or user interaction. The exploit details have been disclosed publicly, and a pull request to address the issue is awaiting acceptance upstream.

Critical Impact
Remote, unauthenticated attackers can inject operating system commands through the write_file tool path, leading to unauthorized command execution on hosts running affected GoClaw releases.

Affected Products

nextlevelbuilder GoClaw versions up to and including 3.11.3
Component: write_file Tool
Affected file: internal/sandbox/fsbridge.go (function FsBridge.WriteFile)

Discovery Timeline

2026-06-01 - CVE-2026-10219 published to the National Vulnerability Database (NVD)
2026-06-01 - Last updated in the NVD database

Technical Details for CVE-2026-10219

Vulnerability Analysis

The vulnerability is classified as OS Command Injection ([CWE-77]). It is triggered through the FsBridge.WriteFile function in internal/sandbox/fsbridge.go, which is invoked by the GoClaw write_file Tool. The function processes caller-supplied data without sufficient sanitization before that data reaches an operating system command execution context. As a result, specially crafted input is interpreted as shell metacharacters or additional command arguments rather than as inert file content or filename data. Public disclosure of the exploit increases the likelihood of opportunistic abuse against unpatched instances.

Root Cause

The root cause is improper neutralization of special elements used in an OS command within the FsBridge.WriteFile code path. Input intended to specify file write operations is concatenated or passed into command execution logic without parameterization or strict validation. Because the write_file tool is reachable through the sandbox bridge, untrusted callers can influence the command string. A pull request providing a fix has been submitted upstream and is awaiting acceptance at the time of publication.

Attack Vector

The vulnerability is exploitable remotely over the network. An attacker submits crafted input to the write_file Tool that reaches FsBridge.WriteFile. Shell metacharacters embedded in the input cause the underlying operating system to execute attacker-controlled commands. Because no authentication is required, any actor with network reachability to the affected component can attempt exploitation. Refer to the GitHub Issue #1121 and GitHub Pull Request #1155 for technical context. Verified proof-of-concept code is not reproduced here; see the VulDB entry for CVE-2026-10219 for additional details.

Detection Methods for CVE-2026-10219

Indicators of Compromise

Unexpected child processes spawned by the GoClaw process tree, particularly shell binaries such as /bin/sh, /bin/bash, or cmd.exe.
Outbound network connections from the GoClaw host to unfamiliar destinations following write_file Tool invocations.
File write operations with filenames or content containing shell metacharacters such as ;, |, &&, backticks, or $().

Detection Strategies

Monitor process creation events where the parent is the GoClaw binary and the child is a shell or interpreter not expected in normal operation.
Log and inspect all calls to the write_file Tool, alerting on payloads containing command separators or substitution syntax.
Correlate suspicious child-process activity with subsequent network egress or filesystem changes outside the intended sandbox directory.

Monitoring Recommendations

Enable verbose audit logging on hosts running GoClaw and forward events to a centralized analytics platform for correlation.
Track GoClaw version inventory across the environment to identify systems running 3.11.3 or earlier.
Review historical telemetry for prior anomalous write_file invocations once the patch is available and disclosure context is fully understood.

How to Mitigate CVE-2026-10219

Immediate Actions Required

Restrict network exposure of GoClaw instances to trusted callers only, using firewall rules or network segmentation.
Disable or gate the write_file Tool where it is not strictly required for operations.
Inspect recent logs for evidence of crafted input to FsBridge.WriteFile and investigate any unexplained command execution.

Patch Information

A vendor-released patched version is not yet available at the time of publication. A fix has been proposed via GitHub Pull Request #1155 and is awaiting acceptance. Track the GoClaw GitHub repository and the linked GitHub Issue #1121 for the official release, and apply the update immediately once published.

Workarounds

Place GoClaw behind an authenticating reverse proxy to prevent unauthenticated network access until a patched release is deployed.
Apply input validation at an upstream layer to reject any write_file payloads containing shell metacharacters such as ;, |, &, `, or $(.
Run GoClaw under a low-privilege account within a constrained container or sandbox to limit the impact of successful command injection.

bash

# Example: restrict GoClaw network exposure to localhost until a patched build is released
# Adjust the interface and port to match your deployment
iptables -A INPUT -p tcp --dport <goclaw_port> ! -s 127.0.0.1 -j DROP