# CVE-2026-100841: MONAI through 1.6.0 PersistentDataset Remote Code Execution via Pickle Cache

> A local attacker with write access to the cache directory can execute arbitrary code via malicious pickle files in MONAI's PersistentDataset.

- **Severity:** High 8.5 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-636w-j999-g7x5, GHSA-wfpp-6gx5-h8xr, PYSEC-2026-4016

## What is CVE-2026-100841?

CVE-2026-100841 is a high-severity unsafe deserialization vulnerability in Project-MONAI MONAI, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In MONAI 1.6.0, PersistentDataset (monai/data/dataset.py) explicitly rejects the combination track_meta=True with weights_only=True, forcing users who cache MetaTensors (the default tensor type in MONAI >= 1.0) to run torch.load(hashfile, weights_only=False). Related cache helpers in monai/data/utils.py also call pickle.loads on cached content and derive cache keys with hashlib.md5. As a result, a local user with write access to a shared or world-writable cache_dir (e.g. /tmp/monai_cache, HPC scratch, ~/.cache/monai) can place a malicious pickle file that is deserialized the next time another user's MONAI pipeline reads the cache, resulting in arbitrary code execution in that user's context. All released versions of the monai pip package are affected; no patched version is available as of the advisory.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-100841?

1 open source package ship an affected version, including monai. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `monai` | PyPI | All versions to 1.6.0-NA | None |

Products: Project-Monai Monai.

## How do I fix CVE-2026-100841?

No fix has been published for CVE-2026-100841 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-100841 being exploited?

There is no known exploitation of CVE-2026-100841 in the wild and no public exploit code.

## Other vulnerabilities in Project-MONAI MONAI

- [CVE-2026-100846](https://insights.sbomify.com/CVE-2026-100846/): MONAI before 1.5.2 Remote Code Execution via Pickle Deserialization (high 8.8)
- [CVE-2026-100844](https://insights.sbomify.com/CVE-2026-100844/): MONAI before 1.6.0 OS Command Injection via dataset_name_or_id (high 8.6)
- [CVE-2026-100840](https://insights.sbomify.com/CVE-2026-100840/): MONAI through 1.6.0 Remote Code Execution via bundle configuration (high 8.5)
- [CVE-2026-100843](https://insights.sbomify.com/CVE-2026-100843/): MONAI before 1.6.0 Remote Code Execution via algo_from_pickle (high 8.5)
- [CVE-2026-100845](https://insights.sbomify.com/CVE-2026-100845/): MONAI before 1.6.0 Remote Code Execution via NumpyReader (high 8.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100841 and fix it if it is affected.

What it is: CVE-2026-100841 is a high-severity unsafe deserialization vulnerability in Project-MONAI MONAI, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-100841 in the wild and no public exploit code.

Affected packages and fixed versions:
- monai (PyPI): affected all versions up to 1.6.0-NA; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100841/ (Markdown: https://insights.sbomify.com/CVE-2026-100841/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100841
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100841
- OSV: https://osv.dev/vulnerability/CVE-2026-100841

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100841/
Summaries are generated and may contain mistakes; the official description above is the record.