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Miggo AIRoot Cause AnalysisThe vulnerability lies in the lack of path confinement when handling user-supplied paths in faf-mcp tools. The analysis of the security patch ae4a5017e18381116c026f7317b43a6dbdd8df73 reveals that several functions were involved in processing these unsafe paths. The core of the issue was in the FafToolHandler.getProjectPath function, which resolved paths without any validation, and the handleFafRead and handleFafWrite functions, which performed file operations using these unvalidated paths. The patch introduces a new module, safe-path.ts, which provides functions (confinePath and confineFileOp) to properly confine paths to the project directory. The vulnerable functions were updated to use these new safe functions, thus mitigating the vulnerability. The presence of a new test file, tests/security-path-confinement.test.ts, further confirms the nature of the vulnerability and the affected code paths by adding specific regression tests for the fixed vulnerabilities.
handleFafReadsrc/handlers/fileHandler.ts
handleFafWritesrc/handlers/fileHandler.ts
FafToolHandler.getProjectPathsrc/handlers/tools.ts
| Package Name | Ecosystem | Vulnerable Versions | First Patched Version |
|---|---|---|---|
| faf-mcp | npm | <= 2.1.2 | 2.1.3 |
faf_read / faf_write) are confined to the project root (cwd + system temp; override with FAF_ALLOWED_ROOTS).../ escapes are rejected; callTool() gains a central PATH-DENIED guard.Upgrade: npm install -g faf-mcp@2.1.3 (or npx faf-mcp).
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.
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).