CVE-2025-53818: 
JavaScript vulnerability analysis and mitigation

CVE-2025-53818 is a command injection vulnerability in the GitHub Kanban MCP Server (@sunwood-ai-labs/github-kanban-mcp-server), a Model Context Protocol (MCP) server for managing GitHub issues in Kanban board format. The vulnerability affects versions up to and including 0.3.0 (and 0.4.0 per ENISA data), with no patched version available as of the advisory publication date. It was disclosed by researcher Liran Tal and published to the GitHub Advisory Database on July 12, 2025, with NVD publication on July 14, 2025. The vulnerability carries a CVSS v4.0 base score of 8.9 (High) (GitHub Advisory).

The root cause is CWE-78 (Improper Neutralization of Special Elements used in an OS Command), classified as OS Command Injection. The vulnerable add_comment tool in src/handlers/comment-handlers.ts uses Node.js's exec API to construct shell commands by directly concatenating user-supplied input — specifically args.issue_number and args.repo — into strings like `gh issue ${command} ${args.issue_number} --repo ${args.repo}` without any sanitization or escaping (GitHub Advisory, comment-handlers.ts). Because exec passes the full string to a shell interpreter, special characters such as ;, &&, or | in user input can break out of the intended command and execute arbitrary OS commands. The attack vector is network-based, requires no privileges, and no user interaction, making it exploitable by any party that can interact with the MCP server or manipulate the LLM into calling the tool with crafted input (e.g., via prompt injection) (GitHub Advisory).

Successful exploitation allows an attacker to execute arbitrary OS commands on the host running the MCP server, with the privileges of the server process. This can result in full system compromise, unauthorized access to sensitive data (including GitHub tokens and credentials available to the process), data destruction, and potential lateral movement within the host environment. The CVSS v4.0 assessment rates confidentiality, integrity, and availability impacts on the vulnerable system as all High (GitHub Advisory).

A proof-of-concept exploitation scenario is described in the advisory: an LLM connected to the MCP server can be manipulated via prompt injection to call the add_comment tool with a payload such as ; rm -rf /tmp;# in the issue_number parameter, causing arbitrary command execution on the server host (GitHub Advisory). The EPSS score is approximately 0.47–1.845% (varying by source), placing it in the 83rd percentile for exploitation likelihood within 30 days. There is no confirmed evidence of in-the-wild exploitation or threat actor attribution at this time, and the vulnerability is not listed in the CISA KEV catalog (GitHub Advisory).

1. Identify the target: Locate a running instance of the GitHub Kanban MCP Server (npm package @sunwood-ai-labs/github-kanban-mcp-server, version ≤ 0.3.0) connected to an LLM agent (e.g., Claude, Cursor).
2. Craft a prompt injection payload: Prepare a malicious input designed to trick the LLM into invoking the add_comment MCP tool with a shell-metacharacter payload in the issue_number field, for example: 1; <malicious_command> ;#.
3. Deliver the payload: Inject the malicious prompt into a context the LLM will process — such as a GitHub issue body, comment, or any user-controlled input the LLM reads — causing it to call add_comment with the crafted issue_number.
4. Trigger command execution: The MCP server's handleAddComment() function passes the unsanitized issue_number directly to Node.js exec, constructing a shell command like gh issue close 1; <malicious_command> ;# --repo owner/repo. The shell interprets the injected command and executes it on the server host.
5. Achieve objective: The injected command runs with the privileges of the MCP server process, enabling data exfiltration, reverse shell establishment, credential theft, or further system compromise (GitHub Advisory, comment-handlers.ts).

• Logs: MCP server logs (console.error output) showing unexpected errors from gh issue commands with unusual arguments; Node.js process logs containing shell metacharacters (;, &&, |) in command strings.
• Process: Unexpected child processes spawned by the Node.js MCP server process (e.g., sh, bash, curl, wget, python) visible via ps or process monitoring tools.
• Network: Unexpected outbound network connections from the MCP server host to unknown external IPs, particularly on non-standard ports, which may indicate reverse shell or data exfiltration activity.
• File System: Unexpected new files, scripts, or modified files in the MCP server working directory or /tmp; missing files if destructive payloads (e.g., rm -rf) were executed.
• Environment: Unexpected access to or exfiltration of environment variables (e.g., GITHUB_TOKEN, GH_TOKEN) that may be present in the MCP server's process environment (GitHub Advisory).

No patched version of @sunwood-ai-labs/github-kanban-mcp-server was available as of the advisory publication date (July 12–15, 2025). The recommended remediation is to replace the use of Node.js exec with execFile, which accepts the command and arguments as separate array elements and does not invoke a shell, preventing injection. Additionally, use the -- double-dash notation to separate command-line flags from user-supplied values. As an immediate workaround, disable or remove the add_comment tool from the MCP server configuration, implement strict input validation (allow only numeric values for issue_number), and apply the principle of least privilege to the server process. Monitor for a patched release from the maintainer (GitHub Advisory).

The vulnerability was disclosed by security researcher Liran Tal, who has published prior work on MCP server command injection and Node.js secure coding practices, referenced in the advisory. The advisory links to Tal's prior research on exploiting MCP servers vulnerable to command injection, indicating this is part of a broader pattern of security issues in the emerging MCP ecosystem. Coverage appeared in security aggregators and newsletters including Secret CISO and TLDR InfoSec, reflecting growing community awareness of MCP server security risks (GitHub Advisory).