CVE-2025-66401 is a critical-severity (CVSS 9.8) OS Command Injection vulnerability in mcp-watch. No vendor fix is recorded yet; mitigation options are listed below.
MCP Watch has a Critical Command Injection in cloneRepo allows Remote Code Execution (RCE) via malicious URL
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66401.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-66401 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
mcp-watchnpmDescription
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.
The code uses child_process.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.
PoC
Install the package or clone the repository.
Run the scanner using the CLI (or invoke scanRepository programmatically).
Provide a malicious URL containing a command separator (e.g., ;, &, or |) and a system command.
payload : npm run scan:github "https://github.com/kapilduraphe/mcp-watch & calc.exe"
Impact
Severity: Critical
CVSS Score: 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) Description: This vulnerability allows an attacker to execute arbitrary code on the machine running the scanner.
If run by a developer locally, it compromises their workstation.
If deployed as a hosted scanning service, it grants the attacker full control over the server (RCE), leading to potential data exfiltration, service disruption, or further lateral movement within the infrastructure.
Context Dependent Risk:
Local CLI : If you run this tool locally on your own machine, you are "hacking yourself." The risk is limited unless you copy-paste a malicious URL sent by someone else (e.g., "Hey, check this repo scan: npm run scan "https://git./..; rm -rf /").
Web Service / CI Pipeline (Critical Risk): If this scanner is deployed as a web service (e.g., "Paste your repo URL to scan"), an attacker can take full control of the server immediately.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | mcp-watch | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mcp-watch, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of mcp-watch has shipped for CVE-2025-66401 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-66401 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-66401. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-66401 in your dependencies?
O3 Security finds CVE-2025-66401 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.