CVE-2026-21851 MONAI has Path Traversal (Zip Slip) in NGC Private Bundle Download
Attackers can exploit a path traversal vulnerability in MONAI's private bundle download to write arbitrary files, potentially leading to code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-21851?
CVE-2026-21851 is a medium-severity path traversal vulnerability in Project-MONAI MONAI, published on 7 Jan 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
MONAI (Medical Open Network for AI) is an AI toolkit for health care imaging. In versions up to and including 1.5.1, a Path Traversal (Zip Slip) vulnerability exists in MONAI's `_download_from_ngc_private()` function. The function uses `zipfile.ZipFile.extractall()` without path validation, while other similar download functions in the same codebase properly use the existing `safe_extract_member()` function. Commit 4014c8475626f20f158921ae0cf98ed259ae4d59 fixes this issue.
Weakness: CWE-22
Which versions are affected by CVE-2026-21851?
3 open source packages ship an affected version, including monai. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
monai PyPI | All versions | 1.5.2 |
monai PyPI | All versions | 1.5.2 |
monai PyPI | All versions | 1.5.2 |
Products include Project-Monai Monai.
How do I fix CVE-2026-21851?
Upgrade monai to 1.5.2 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-21851 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21851 exists.
Other vulnerabilities in Project-MONAI MONAI
- CVE-2026-100846 MONAI before 1.5.2 Remote Code Execution via Pickle Deserialization
- CVE-2026-100844 MONAI before 1.6.0 OS Command Injection via dataset_name_or_id
- CVE-2026-100840 MONAI through 1.6.0 Remote Code Execution via bundle configuration
- CVE-2026-100841 MONAI through 1.6.0 PersistentDataset Remote Code Execution via Pickle Cache
- CVE-2026-100843 MONAI before 1.6.0 Remote Code Execution via algo_from_pickle
Sources
Also known as GHSA-9rg3-9pvr-6p27, PYSEC-2026-1678.