{"id":"GHSA-j4r7-8ph4-43g3","aliases":[],"url":"https://o3.security/vulnerability/GHSA-j4r7-8ph4-43g3","summary":"faf-mcp has an arbitrary local file read/write via unconfined `path` argument in FAF tools","details":"### Summary\n`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.\n\n### Affected tools\nThe 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.\n\n### Impact\nAn 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).\n\n### Patches\nFixed in **2.1.3** by confining every caller-supplied `path` before any filesystem access (`safe-path.ts`):\n- Reads are restricted to `.faf` / `.fafm` context files, so non-context files (secrets) are refused regardless of directory.\n- General file ops (`faf_read` / `faf_write`) are confined to the project root (cwd + system temp; override with `FAF_ALLOWED_ROOTS`).\n- Paths are canonicalized through symlinks (closing the symlink bypass); absolute paths and `../` escapes are rejected; `callTool()` gains a central PATH-DENIED guard.\n\nUpgrade: `npm install -g faf-mcp@2.1.3` (or `npx faf-mcp`).\n\n### Workarounds\nIf 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.\n\n### Credits\nIdentified 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).","published":"2026-08-19T19:15:13Z","modified":"2026-08-19T19:30:06.662039056Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"faf-mcp","fixedVersion":"2.1.3"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/Wolfe-Jam/faf-mcp/security/advisories/GHSA-j4r7-8ph4-43g3"},{"type":"PACKAGE","url":"https://github.com/Wolfe-Jam/faf-mcp"},{"type":"WEB","url":"https://github.com/Wolfe-Jam/faf-mcp/releases/tag/v2.1.3"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-19T19:30:06.662039056Z"}}