GHSA-j4r7-8ph4-43g3: Faf mcp Faf-mcp Has An Arbitrary Local Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-j4r7-8ph4-43g3",
  "modified" : "2026-08-19T19:15:13Z",
  "published" : "2026-08-19T19:15:13Z",
  "aliases" : [ ],
  "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).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "faf-mcp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.1.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.1.2"
    }
  } ],
  "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"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-22", "CWE-73" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-19T19:15:13Z",
    "nvd_published_at" : null
  }
}