GHSA-J7H9-2JH7-G967: GHSA-j7h9-2jh7-g967: Path Policy Bypass and Timing Side-Channel in mcp-ssh-tool

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GHSA-j7h9-2jh7-g967: Path Policy Bypass and Timing Side-Channel in mcp-ssh-tool

Vulnerability ID: GHSA-J7H9-2JH7-G967
CVSS Score: 8.7
Published: 2026-05-07

The mcp-ssh-tool npm package prior to version 2.1.1 contains two significant security flaws: an incomplete path policy enforcement mechanism that permits directory traversal and local path bypasses (CWE-22), and an observable timing differential in bearer token authentication (CWE-208).

TL;DR

mcp-ssh-tool <= 2.1.0 suffers from path traversal and policy bypass due to improper prefix checking, alongside an authentication timing side-channel. Upgrading to 2.1.1 resolves both issues.

Technical Details

Vulnerability IDs: GHSA-j7h9-2jh7-g967
CVSS v4.0 Base Score: 8.7 (High)
Primary CWEs: CWE-22 (Path Traversal), CWE-208 (Observable Timing Differential)
Attack Vector: Network
Privileges Required: None
Exploit Status: No public PoC identified
Affected Versions: <= 2.1.0
Fixed Version: 2.1.1

Affected Systems

mcp-ssh-tool npm package
mcp-ssh-tool: <= 2.1.0 (Fixed in: 2.1.1)

Mitigation Strategies

Upgrade mcp-ssh-tool to a patched version
Restrict network exposure of the HTTP transport layer
Audit filesystem policies for prefix collisions
Implement strict rate limiting to hinder timing side-channel attacks

Remediation Steps:

Identify the current version of mcp-ssh-tool using npm list -g mcp-ssh-tool.
Upgrade the package using npm install -g mcp-ssh-tool@latest.
Restart the mcp-ssh-tool service to load the updated module.
Review access logs for repeated failed authentication attempts that may indicate token brute-forcing.
Review file transfer logs for suspicious paths involving '..' sequences or unusual prefix patterns.