CVE-2025-66401: MCP Watch has a Critical Command Injection in cloneRepo allows Remote Code Execution (RCE) via malicious URL

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 2.2%, percentile 83: FIRST’s model estimates a 2.2% chance of exploitation activity in the next 30 days, higher than 83% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes mcp-watch (npm) <= 0.1.2, no fixed version listed. Check your lockfile, including transitive dependencies.

What it is

MCP Watch is a comprehensive security scanner for Model Context Protocol (MCP) servers. In 0.1.2 and earlier, the MCPScanner class contains a critical Command Injection vulnerability in the cloneRepo method. The application passes the user-supplied githubUrl argument directly to a system shell via execSync without sanitization. This allows an attacker to execute arbitrary commands on the host machine by appending shell metacharacters to the URL.

From the GitHub advisory

Summary The MCPScanner class contains a critical Command Injection vulnerability in the cloneRepo method. The application passes the user-supplied githubUrl argument directly to a system shell via execSync without sanitization. This allows an attacker to execute arbitrary commands on the host machine by appending shell metacharacters to the URL.

Details The vulnerability exists in the src/scanner/MCPScanner.ts file within the cloneRepo method.

https://github.com/kapilduraphe/mcp-watch/blob/0fca7228bd313ae5aa938d61311377e88ce6e682/src/scanner/McpScanner.ts#L181

The code uses childprocess.execSync to execute a git clone command:

Because execSync spawns a shell (defaulting to /bin/sh on Unix or cmd.exe on Windows), any shell metacharacters present in the url argument will be interpreted by the shell. The application does not validate that the url is a valid Git URL, nor does it sanitize input for shell metacharacters.

Weakness type: CWE-78.

Product: mcp-watch (npm) · Assigned by: GitHub_M · Published: 2025-12-01

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 2.23% probability of exploitation activity in the next 30 days; percentile 83.

Timeline

• 2025-12-01 — CVE record published by GitHub_M
• 2025-12-02 — CVE record last updated
• 2025-12-02 — GitHub-reviewed advisory GHSA-27m7-ffhq-jqrm published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-27m7-ffhq-jqrm github.com
2. CVE.org record CVE-2025-66401 cve.org
3. NVD entry CVE-2025-66401 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

Critical npm advisories · Today’s Security Digest