Vulnerability Summary

CVE ID: CVE-2026-0756
Component: github-kanban-mcp-server (@sunwood-ai-labs/github-kanban-mcp-server)
Vulnerability Type: OS Command Injection
Attack Class: Unauthenticated Remote Code Execution
Severity: Critical
CVSS Score: 9.8 (Network exploitable, no privileges, no user interaction)
Exploitability: High
Exploit Availability: Publicly described exploitation techniques exist; proof-of-concept style payloads are trivial to construct
Impact: Full compromise of the hosting system (confidentiality, integrity, availability)

Overview

A critical command injection vulnerability exists in github-kanban-mcp-server due to unsafe execution of system commands constructed from user-supplied input. The server exposes MCP tooling endpoints that internally invoke the GitHub CLI (gh) using Node.js shell execution functions. Because untrusted input is directly concatenated into shell commands, it becomes possible for a remote attacker to inject arbitrary operating system commands.

The vulnerability can be exploited without authentication and does not require any prior access to the system. Successful exploitation results in arbitrary command execution with the privileges of the MCP server process, which may include access to source code, credentials, network resources, or CI/CD infrastructure.

Root Cause Analysis

The issue originates from the use of Node.js exec or execAsync APIs to invoke GitHub CLI commands. These APIs execute commands through a system shell. In multiple tool handlers, parameters such as issue number, repository name, or comment body are accepted from client requests and directly embedded into a command string.

Because the shell interprets special characters, any attacker-controlled field that includes shell metacharacters can alter the intended command flow. The absence of strict input validation or argument separation enables classic OS command injection.

This behavior aligns with CWE-78: Improper Neutralization of Special Elements used in an OS Command.

Exploitation Details (Educational)

Exploitation occurs when an attacker submits crafted input containing shell control characters such as ;, &&, |, backticks, or $() within parameters expected to be simple values.

The typical exploitation flow is as follows:

1. A malicious request is sent to an exposed MCP endpoint that triggers a GitHub CLI operation.
2. User-controlled input is interpolated into a shell command.
3. The shell interprets injected metacharacters.
4. Arbitrary attacker-defined commands are executed on the server.

Examples of injected behavior include downloading and executing remote scripts, opening reverse shells, modifying files, or extracting secrets. These examples are provided strictly for understanding detection patterns and should never be executed.

Proof-of-Concept Status

Public advisories and security write-ups describe the vulnerable execution pattern and demonstrate how shell metacharacters can be used to achieve command execution. Due to the simplicity of the flaw, creating a working exploit does not require advanced techniques.

Any proof-of-concept activity should only be conducted in controlled test environments for defensive validation and education.

Detection and Monitoring Guidance

Recommended Log Sources

To reliably detect exploitation attempts or successful compromise, the following log sources should be collected and centrally monitored:

• Operating system process creation logs (Linux auditd, Windows Sysmon)
• Application logs from the MCP server
• Web server or API access logs
• Network egress logs from the MCP server host
• File system activity logs for temporary and application directories

Indicators of Compromise

Potential indicators include:

• Node.js processes spawning child processes with unexpected command-line arguments
• GitHub CLI (gh) executions containing shell metacharacters
• Sudden outbound network connections from the MCP server
• Creation of shell or script files in temporary directories
• Execution of utilities such as bash, sh, curl, wget, nc, or python -c by the MCP process

Detection Rules

Rule 1: Suspicious Shell Characters in GitHub CLI Execution

title: Suspicious GitHub CLI Execution with Shell Metacharacters
logsource:
  category: process_creation
detection:
  selection:
    parent_process: node
    command_line|contains: "gh"
    command_line|matches_regex: "[;&|`$()]"
condition: selection
level: high

This rule identifies shell control characters embedded in GitHub CLI commands executed by Node.js, which is not expected in legitimate usage.

Rule 2: Web Request Followed by Unexpected Command Execution

title: Web Request Correlated with Suspicious Child Process
logsource:
  category: process_creation
detection:
  selection1:
    parent_process: node
  selection2:
    command_line|contains_any:
      - "bash"
      - "sh"
      - "curl"
      - "wget"
      - "nc"
      - "python -c"
condition: selection1 and selection2
level: critical

This rule helps detect post-exploitation activity where shell utilities are spawned as a result of an API request.

Rule 3: Unexpected Script Creation by MCP Server

title: Unexpected Script Files Created by Node Server
logsource:
  category: file_event
detection:
  selection:
    process_name: node
    file_extension:
      - ".sh"
      - ".py"
      - ".tmp"
condition: selection
level: medium

This rule detects script staging commonly associated with command injection exploitation.

Mitigation and Hardening Recommendations

Until a patched version is deployed, the following mitigations are strongly advised:

• Restrict external network access to MCP server endpoints.
• Apply strict firewall and access control rules.
• Run the MCP server under a least-privileged service account.
• Monitor and alert on command execution anomalies.
• Disable or limit high-risk MCP tools if possible.

Secure Development Fix Guidance

Long-term remediation requires eliminating shell interpretation entirely:

• Replace exec or execAsync with execFile or spawn.
• Pass arguments as arrays rather than concatenated strings.
• Enforce strict allow-list validation for all user-supplied parameters.
• Avoid passing free-form text to system commands.
• Apply proper error handling and logging around command execution.

Official Patch / Upgrade Advisory

The authoritative source for remediation guidance and fixed versions is provided below. This is the only official reference that should be followed for patching and upgrades:

https://github.com/advisories/GHSA-298v-qmqm-hfrx

Final Takeaway

CVE-2026-0756 represents a severe and easily exploitable vulnerability that can lead to full system compromise. Any exposed instance of github-kanban-mcp-server should be treated as high risk until patched. Defensive monitoring, network isolation, and prompt upgrades are essential to reduce exposure.