Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-j4r7-8ph4-43g3
faf-mcpSummary
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/.fafmcontext 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 withFAF_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).
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard