CVE-2026-31040: stata-mcp RCE Vulnerability Explained

CVE-2026-31040 Overview

A critical command injection vulnerability was identified in stata-mcp prior to version v1.13.0 where insufficient validation of user-supplied Stata do-file content can lead to arbitrary command execution. The vulnerability stems from the lack of sanitization when processing do-files, allowing attackers to leverage Stata's shell-escape directives (!cmd or shell cmd) to execute arbitrary operating system commands on the underlying host.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary commands on systems running vulnerable versions of stata-mcp, potentially leading to complete system compromise, data exfiltration, or lateral movement within the network.

Affected Products

• stata-mcp versions prior to v1.13.0

Discovery Timeline

• 2026-04-08 - CVE-2026-31040 published to NVD
• 2026-04-09 - Last updated in NVD database

Technical Details for CVE-2026-31040

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code / Code Injection). The stata-mcp application processes Stata do-files without adequate validation of their content before execution. Stata's scripting language includes shell-escape functionality that allows direct execution of operating system commands through directives prefixed with ! or the shell keyword.

When a malicious actor supplies a crafted do-file containing these shell-escape directives, the application passes the content directly to the Stata interpreter, which in turn executes the embedded OS commands with the privileges of the running process. The network-accessible nature of this attack surface, combined with no authentication requirements and no user interaction needed, makes this vulnerability particularly severe.

Root Cause

The root cause is the absence of input validation in the do.py module within the src/stata_mcp/core/stata/stata_do/ directory. Prior to the patch, the application would read and execute do-file content without checking for dangerous shell-escape tokens. The Stata statistical software includes built-in functionality to execute shell commands (using !command or shell command syntax), which was being exploited through unvalidated user input.

Attack Vector

An attacker can exploit this vulnerability by supplying a malicious Stata do-file containing shell-escape directives to the stata-mcp service over the network. Since no authentication or user interaction is required, an attacker can craft a do-file with embedded shell commands that will be executed when the file is processed.

For example, a do-file containing:

// Legitimate Stata commands above
!whoami
shell cat /etc/passwd > /tmp/exfil.txt

The security patch introduced in commit 52413ce adds validation to reject do-files containing these dangerous patterns:

        # ===== Initial security guard: validate do-file content =====
        def _validate_dofile_content(text: str) -> None:
            """
            Initial security guard: reject Stata shell-escape directives
            like `!cmd` or `shell cmd` to prevent OS command execution.
            """
            dangerous_tokens = ["\n!", "\nshell "]
            for token in dangerous_tokens:
                if token in text:
                    raise ValueError(
                        "Shell-escape commands (!cmd or shell cmd) "
                        "are disabled for security reasons."
                    )

        try:
            # Load the do-file content and validate before execution
            with open(dofile_path, "r", encoding="utf-8") as f:
                dofile_content = f.read()
            _validate_dofile_content(dofile_content)
        except Exception as e:
            return f"There is a security in {dofile_path}, error: {e}"
        # ===== End of initial security guard =====

Source: GitHub Commit Update

Detection Methods for CVE-2026-31040

Indicators of Compromise

• Unexpected shell commands or processes spawned by the stata-mcp application or Stata interpreter
• Do-files containing ! prefixed commands or shell directives in upload directories or processing queues
• Unusual network connections or file system modifications originating from the stata-mcp process
• Log entries showing errors related to do-file validation or execution failures with shell-escape keywords

Detection Strategies

• Implement file content inspection rules to detect do-files containing shell-escape patterns (!cmd, shell cmd)
• Monitor process creation events for unexpected child processes spawned by stata-mcp or Stata binaries
• Deploy network detection rules to identify exploitation attempts targeting stata-mcp endpoints
• Configure endpoint detection to alert on command injection patterns in file uploads

Monitoring Recommendations

• Enable verbose logging for the stata-mcp application to capture all do-file processing attempts
• Implement real-time file integrity monitoring on directories where do-files are uploaded or processed
• Set up alerts for any processes spawned by stata-mcp that are not expected Stata executables
• Monitor outbound network connections from hosts running stata-mcp for data exfiltration attempts

How to Mitigate CVE-2026-31040

Immediate Actions Required

• Upgrade stata-mcp to version v1.13.0 or later immediately
• If immediate patching is not possible, restrict network access to the stata-mcp service to trusted sources only
• Audit existing do-files for any suspicious shell-escape directives
• Review system logs for evidence of prior exploitation attempts

Patch Information

The vulnerability has been addressed in stata-mcp version v1.13.0. The fix introduces a validation function _validate_dofile_content() that checks do-file content for dangerous shell-escape tokens before execution. Users should upgrade to the patched version available at the GitHub Release v1.13.0.

Additional details about the vulnerability and fix can be found in:

• GitHub Issue Discussion
• GitHub Pull Request
• GitHub Commit Update

Workarounds

• Implement network-level access controls to restrict which hosts can communicate with the stata-mcp service
• Deploy a Web Application Firewall (WAF) or input filtering proxy to inspect and block do-files containing shell-escape patterns
• Run stata-mcp in a sandboxed environment or container with restricted system access and no network egress
• Temporarily disable the do-file processing functionality if it is not business-critical

# Example: Restrict network access to stata-mcp using iptables
# Allow only trusted internal network (adjust IP range as needed)
iptables -A INPUT -p tcp --dport 8080 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP