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How the mentioned CVE works
The vulnerability resides in the media route handlers of `@tinacms/cli` (specifically dev mode).
A lexical path validation function—resolveWithinBase / resolveStrictlyWithinBase—uses `path.resolve` and `startsWith` to check if a user‑supplied path stays inside the configured media root.
However, these checks operate only on the string representation and do not resolve filesystem symlinks or junctions.
If an attacker can place (or find) a symbolic link or junction inside the media root that points to a directory outside, the validation passes because the lexical path appears to be inside the root.
After validation, the code performs actual filesystem operations (fs.readdir, fs.createWriteStream, fs.remove) using the already validated path string.
Because the underlying filesystem resolves the link, operations are performed on the target directory outside the media root.
This leads to three concrete attacks:
- Out‑of‑root listing – `GET /media/list/…` can read any directory reachable via the link.
- Out‑of‑root write – `POST /media/upload/…` can write arbitrary files outside the media root.
- Out‑of‑root delete – `DELETE /media/…` can delete files outside the media root.
The attack is reproducible on any platform where the media tree contains a link, and is especially relevant in self‑hosted or development workflows where such links may be present.
dailycve form
Platform: @tinacms/cli
Version: pre‑patch versions
Vulnerability: Path traversal via symlink
Severity: Medium
date: 2026-03-31
Prediction: Patch within 2 weeks
What Undercode Say:
Simulate link under media root (Linux/macOS)
mkdir -p public/uploads/outside
ln -s ../../outside public/uploads/pivot
Confirm path validation passes
node -e "
const path = require('path');
const base = path.resolve('public/uploads');
const userPath = 'pivot/secret.txt';
const resolved = path.resolve(path.join(base, userPath));
console.log(resolved.startsWith(base + path.sep)); // true
"
Exploit via curl (assuming dev server on localhost:3000)
curl 'http://localhost:3000/media/list/pivot' lists outside/secret.txt
curl -X POST -F "[email protected]" 'http://localhost:3000/media/upload/pivot/'
curl -X DELETE 'http://localhost:3000/media/delete/pivot/secret.txt'
Exploit:
- Identify an existing symlink/junction under the media root, or create one if the application allows uploading of symbolic links.
- Use that link name as the first path segment in any media API call (list, upload, delete).
- The lexical validation accepts the path; the filesystem operations then follow the link, accessing or modifying files outside the intended media directory.
Protection from this CVE
- Apply the official fix once released (currently in progress).
- Until patched, avoid using symlinks or junctions inside the media root.
- If self‑hosting, run the media server in a restricted container or with filesystem permissions that limit the impact of a traversal.
- Manually patch by replacing lexical checks with canonical path resolution using `fs.realpath` on both the base and the user‑supplied path, then compare.
Impact
- Confidentiality: Unauthorized listing of arbitrary files on the server.
- Integrity: Arbitrary file writes (upload) and deletions outside the media root.
- Availability: Could delete critical system files if the server user has write permissions.
- Scope: All deployments of `@tinacms/cli` where the media tree contains a symlink or junction, including development and self‑hosted environments.
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Sources:
Reported By: github.com
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