---
id: GHSA-j4r7-8ph4-43g3
title: >-
  faf-mcp has an arbitrary local file read/write via unconfined `path` argument
  in FAF tools
summary: >-
  faf-mcp has an arbitrary local file read/write via unconfined `path` argument
  in FAF tools
severity: high
cvss: 7.5
cwe:
  - CWE-22
  - CWE-73
  - CWE-200
vendor: faf-mcp
product: faf-mcp
ecosystem: npm
affected:
  - faf-mcp <= 2.1.2
patched:
  - faf-mcp 2.1.3
published: '2026-08-19'
updated: '2026-08-19'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-j4r7-8ph4-43g3'
references:
  - url: >-
      https://github.com/Wolfe-Jam/faf-mcp/security/advisories/GHSA-j4r7-8ph4-43g3
  - url: 'https://github.com/Wolfe-Jam/faf-mcp/releases/tag/v2.1.3'
  - url: 'https://github.com/advisories/GHSA-j4r7-8ph4-43g3'
tags:
  - ghsa
  - npm
ingestedAt: '2026-08-19T19:44:03.367Z'
---

## Overview

### Summary
`faf-mcp` MCP tools accept a caller-controlled `path` argument and resolve it (`~` expansion + `path.resolve()`) straight into a filesystem read/write **without confining it to a trusted project directory**. An absolute path or `../` traversal is resolved and used as-is, so the server process can be made to read — and, via the file tools, write — files outside the intended `.faf` project context. The only remaining limit is OS file permissions.

### Affected tools
The shared `getProjectPath()` chokepoint (feeding the `.faf` tools) and the general-purpose `faf_read` / `faf_write` file tools resolved a caller path straight into a read/write with no confinement (denylist-only); an absolute path still reached home-directory secrets, and `faf_write` could write outside the project.

### Impact
An MCP client — or an LLM prompt-injected via attacker-controlled content (a web page, README, ticket, or `.faf`) into issuing a tool call — can read any file the server process can read: SSH keys (`~/.ssh/id_rsa`), cloud credentials (`~/.aws/credentials`), `.env` files, source, `/etc/passwd`; and `faf_write` could write outside the project. This is a sensitive-information-disclosure (CWE-200) primitive that far exceeds the declared `.faf` project-context scope. The server runs over stdio, so the read/write is reached by a crafted tool call (e.g. a prompt-injected agent processing attacker-controlled content).

### Patches
Fixed in **2.1.3** by confining every caller-supplied `path` before any filesystem access (`safe-path.ts`):
- Reads are restricted to `.faf` / `.fafm` context files, so non-context files (secrets) are refused regardless of directory.
- General file ops (`faf_read` / `faf_write`) are confined to the project root (cwd + system temp; override with `FAF_ALLOWED_ROOTS`).
- Paths are canonicalized through symlinks (closing the symlink bypass); absolute paths and `../` escapes are rejected; `callTool()` gains a central PATH-DENIED guard.

Upgrade: `npm install -g faf-mcp@2.1.3` (or `npx faf-mcp`).

### Workarounds
If you cannot upgrade immediately, run the server only against trusted local projects, and set `FAF_ALLOWED_ROOTS` (patched versions) to a single project directory for a hard directory boundary.

### Credits
Identified by the maintainers during a sibling-server audit prompted by the coordinated disclosure of the same class of issue in `grok-faf-mcp` by **Zhihao Zhang** (Worcester Polytechnic Institute).

## Affected packages

- `faf-mcp <= 2.1.2`

## Remediation

Upgrade to a patched release:

- `faf-mcp 2.1.3`