Listen to this Post
How CVE-2026-XXXX Works
The vulnerability exists in `jupyterlab-git` version 0.53.0, where the `GitHandler.prepare()` method uses `fnmatch.fnmatchcase()` to enforce admin-configured excluded_paths. This function performs a case-sensitive pattern match, which is problematic on case-insensitive filesystems like macOS APFS and Windows NTFS.
An authenticated attacker can bypass the exclusion check by simply changing the case of characters in the URL path. For example, if the admin excludes /project/secrets, a request to `/project/Secrets` will not match the exclusion pattern because `fnmatch.fnmatchcase()` treats them as different strings.
The downstream function `url2localpath()` then resolves the case-varied path to the same actual directory on disk, granting the attacker access to the excluded content. This bypass allows reading file content, viewing git status, logs, and diffs, and enumerating commits in the protected directory.
The root cause is the unconditional case sensitivity of fnmatch.fnmatchcase(), which does not account for the underlying filesystem’s case sensitivity. The fix involves using `fnmatch.fnmatch()` with `os.path.normcase()` or manually lowercasing both the path and the pattern before comparison.
DailyCVE Form
Platform: JupyterLab-Git
Version: 0.53.0
Vulnerability: Path Traversal (Case-Insensitive Bypass)
Severity: Medium
Date: 2026-04-30
Prediction: 2026-05-15
What Undercode Say
The following analysis and commands demonstrate the vulnerability and its impact:
Check if the system is case-insensitive (macOS/Windows) On macOS, APFS is case-insensitive by default On Windows, NTFS is case-insensitive Install the vulnerable version pip install 'jupyterlab-git==0.53.0' Run the Proof of Concept (POC) script python poc.py
The POC script (as provided in the ) performs the following steps:
1. Sets up a temporary Jupyter server with excluded_paths = ["/project/secrets", "/project/secrets/"].
2. Creates a Git repository with a `secrets` directory containing a sensitive file.
3. Sends a request to the excluded path (lowercase) and confirms it returns 404.
4. Sends a request to the case-varied path (uppercase) and confirms it returns 200.
5. Exfiltrates the secret file content via the `/content` endpoint.
Exploit
The exploit is straightforward and requires only an authenticated session. The attacker can bypass the exclusion by changing the case of the path segment in the URL. For example:
POST /git/project/Secrets/status HTTP/1.1
Host: 127.0.0.1:18895
Authorization: token xtoken
Content-Type: application/json
{}
This request will return a 200 OK response, whereas the lowercase version would return 404. The attacker can then read files:
POST /git/project/Secrets/content HTTP/1.1
Host: 127.0.0.1:18895
Authorization: token xtoken
Content-Type: application/json
{"filename": "./cred.txt", "reference": {"git": "HEAD"}}
The response will contain the contents of cred.txt, exfiltrating the secret.
Protection
The fix involves modifying the comparison logic in `jupyterlab_git/handlers.py` to be case-insensitive on case-insensitive filesystems. Two approaches are recommended:
1. Using `fnmatch.fnmatch()` with `os.path.normcase()`:
if fnmatch.fnmatch(os.path.normcase(path), os.path.normcase(excluded_path)): raise tornado.web.HTTPError(404)
2. Manual lowercasing:
if fnmatch.fnmatch(path.lower(), excluded_path.lower()): raise tornado.web.HTTPError(404)
Users should upgrade to a patched version once available. As a temporary workaround, administrators can restrict access to the Jupyter server or use a reverse proxy with case-sensitive path normalization.
Impact
- Confidentiality: An authenticated attacker can read files in excluded directories, potentially exposing sensitive information such as credentials, configuration files, or proprietary code.
- Integrity: While the primary impact is read access, the attacker could also view git logs and diffs, which might reveal further sensitive information or code changes.
- Availability: No direct availability impact, but the bypass could lead to further exploitation if combined with other vulnerabilities.
- Scope: Affects all deployments of `jupyterlab-git` 0.53.0 on case-insensitive filesystems (macOS, Windows). Linux systems with case-sensitive filesystems are not vulnerable to this specific bypass.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
