# GHSA-rr55-jp92-8wp2: claude-faf-mcp has an arbitrary local file read/write via unconfined `path` argument in FAF tools

> Attackers can read or write arbitrary files outside the project directory via path traversal in claude-faf-mcp, exposing sensitive credentials and data.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 19 Aug 2026

## What is GHSA-rr55-jp92-8wp2?

GHSA-rr55-jp92-8wp2 is a path traversal vulnerability in claude-faf-mcp, published on 19 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

### Summary
`claude-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 **5.7.2** 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 claude-faf-mcp@5.7.2` (or one-click `.mcpb` install).

### 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).

## Which versions are affected by GHSA-rr55-jp92-8wp2?

2 open source packages ship an affected version, including claude-faf-mcp.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `claude-faf-mcp` | npm | All versions | 5.7.2 |
| `claude-faf-mcp` | npm | All versions | 5.7.2 |

## How do I fix GHSA-rr55-jp92-8wp2?

Upgrade claude-faf-mcp to 5.7.2 or later.

## Is GHSA-rr55-jp92-8wp2 being exploited?

There is no known exploitation of GHSA-rr55-jp92-8wp2 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-rr55-jp92-8wp2 and fix it if it is affected.

What it is: GHSA-rr55-jp92-8wp2 is a path traversal vulnerability in claude-faf-mcp, published on 19 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of GHSA-rr55-jp92-8wp2 in the wild and no public exploit code.

Affected packages and fixed versions:
- claude-faf-mcp (npm): affected all versions; fixed in 5.7.2
- claude-faf-mcp (npm): affected all versions; fixed in 5.7.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-rr55-jp92-8wp2/ (Markdown: https://insights.sbomify.com/GHSA-rr55-jp92-8wp2/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-rr55-jp92-8wp2

---
From sbomify Insights: https://insights.sbomify.com/GHSA-rr55-jp92-8wp2/
Summaries are generated and may contain mistakes; the official description above is the record.