GHSA-gmfx-5g6x-rr72 - ApostropheCMS: Path traversal in uploadfs

## Summary The `uploadfs` library's local storage backend does not validate or sanitize user-supplied paths. The `prefixPath()` helper only strips double slashes (`//`) and the backend performs direct string concatenation (`uploadsPath + path`). An attacker can inject `../` sequences to escape the intended uploads directory, resulting in arbitrary file read, write, and delete on the host filesystem. --- ## Details ### Root Cause `packages/uploadfs/uploadfs.js:652-655` https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/uploadfs.js#L652-L655 ```javascript function prefixPath(path) { // Resolve any double // that results from the prefix return (self.prefix + path).replace(/\/\//g, '/'); } ``` `packages/uploadfs/lib/storage/local.js` https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L92-L95 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L102-L104 https://github.com/apostrophecms/apostrophe/blob/main/packages/uploadfs/lib/storage/local.js#L106-L108 ```javascript copyIn: function(localPath, path, options, callback) { const uploadPath = uploadsPath + path; // [VULNERABLE] return copyFile(localPath, uploadPath, callback); }, streamOut: function(path, options) { return fs.createReadStream(uploadsPath + path); // [VULNERABLE] }, remove: function(path, callback) { const uploadPath = uploadsPath + path; // [VULNERABLE] fs.unlink(uploadPath, callback); ``` - `prefixPath()` does **not** normalize paths or reject `../`. - The local backend concatenates the path directly into the filesystem call. - Node.js resolves `/app/uploads/../../../tmp/pwned.txt` → `/tmp/pwned.txt`. --- ## Proof of Concept (PoC) Here is the poc files https://drive.proton.me/urls/AKY4V5S0JR#Vw6XJdVCZafk ### Build and run ```bash docker load < apostrophe-uploadfs-poc.tar docker run -d -p 3000:3000 --name uploadfs-poc apostrophe-uploadfs-poc python3 exploit.p