# CVE-2026-100846: MONAI before 1.5.2 Remote Code Execution via Pickle Deserialization

> Attackers can execute arbitrary code by supplying malicious pickle files to the algo_from_pickle function in MONAI.

- **Severity:** High 8.8 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 27 Sep 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-89gg-p5r5-q6r4, GHSA-cvqf-4876-w239, PYSEC-2026-4021

## What is CVE-2026-100846?

CVE-2026-100846 is a high-severity unsafe deserialization vulnerability in Project-MONAI MONAI, published on 27 Sep 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### Official description

MONAI before 1.5.2 contains a deserialization of untrusted data vulnerability in the algo_from_pickle function in monai/auto3dseg/utils.py. The function reads a .pkl file and passes its contents to pickle.loads without validating the data source or content. If an application invokes algo_from_pickle on an attacker-supplied pickle file, an object defining __reduce__ is executed during deserialization, resulting in arbitrary code execution in the context of the application.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-100846?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `monai` | PyPI | All versions | 1.5.2 |
| `monai` | PyPI | All versions | 1.6.0 |
| `monai` | PyPI | All versions | 1.6.0 |

Products: Project-Monai Monai.

## How do I fix CVE-2026-100846?

Upgrade monai to a fixed version for your release line: 1.5.2 or 1.6.0.

## Is CVE-2026-100846 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100846 exists.

## Other vulnerabilities in Project-MONAI MONAI

- [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-2026-100841](https://insights.sbomify.com/CVE-2026-100841/): MONAI through 1.6.0 PersistentDataset Remote Code Execution via Pickle Cache (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-2026-100846 and fix it if it is affected.

What it is: CVE-2026-100846 is a high-severity unsafe deserialization vulnerability in Project-MONAI MONAI, published on 27 Sep 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100846 exists.

Affected packages and fixed versions:
- monai (PyPI): affected all versions; fixed in 1.5.2
- monai (PyPI): affected all versions; fixed in 1.6.0
- monai (PyPI): affected all versions; fixed in 1.6.0

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-2026-100846/ (Markdown: https://insights.sbomify.com/CVE-2026-100846/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100846
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100846
- OSV: https://osv.dev/vulnerability/CVE-2026-100846

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100846/
Summaries are generated and may contain mistakes; the official description above is the record.