# CVE-2026-42521: Jenkins Matrix Authorization Strategy Plugin: Unsafe deserialization allows invocation of parameterless constructors

> Attackers with configure permissions can instantiate arbitrary classes via unsafe deserialization, potentially leading to information disclosure.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Apr 2026
- **Updated:** 29 Apr 2026
- **Also known as:** GHSA-jp9r-mmhw-vff3, MINI-296j-xcj5-c6fx, MINI-48r4-8gfg-hrv3, MINI-8jp9-r8p3-7c27, MINI-vmw5-xhj6-w276, MINI-w3rq-69qj-f5j9, MINI-wj36-455g-926q, MINI-wq9h-4xfh-w9qr

## What is CVE-2026-42521?

CVE-2026-42521 is a medium-severity unsafe deserialization vulnerability in Jenkins Matrix Authorization Strategy Plugin, published on 29 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Jenkins Matrix Authorization Strategy Plugin 2.0-beta-1 through 3.2.9 (both inclusive) invokes parameterless constructors of classes specified in configuration when deserializing inheritance strategies, without restricting the classes that can be instantiated, allowing attackers with Item/Configure permission to instantiate arbitrary types, which may lead to information disclosure or other impacts depending on the classes available on the classpath.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-42521?

2 open source packages ship an affected version, including org.jenkins-ci.plugins:matrix-auth. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.jenkins-ci.plugins:matrix-auth` | Maven | From 2.0-beta-1 | 3.2.10 |
| `org.jenkins-ci.plugins:matrix-auth` | Maven | From 2.0-beta-1 | 3.2.10 |

Products: Jenkins Matrix Authorization Strategy.

## How do I fix CVE-2026-42521?

Upgrade org.jenkins-ci.plugins:matrix-auth to 3.2.10 or later.

## Is CVE-2026-42521 being exploited?

There is no known exploitation of CVE-2026-42521 in the wild and no public exploit code.

## Other vulnerabilities in Jenkins Matrix Authorization Strategy Plugin

- [CVE-2021-21623](https://insights.sbomify.com/CVE-2021-21623/): Incorrect permission checks in Jenkins Matrix Authorization Strategy Plugin may allow accessing some items (medium 6.5)
- [CVE-2020-2226](https://insights.sbomify.com/CVE-2020-2226/): Stored XSS vulnerability in Jenkins Matrix Authorization Strategy Plugin (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42521 and fix it if it is affected.

What it is: CVE-2026-42521 is a medium-severity unsafe deserialization vulnerability in Jenkins Matrix Authorization Strategy Plugin, published on 29 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42521 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.jenkins-ci.plugins:matrix-auth (Maven): affected from 2.0-beta-1; fixed in 3.2.10
- org.jenkins-ci.plugins:matrix-auth (Maven): affected from 2.0-beta-1; fixed in 3.2.10

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-2026-42521/ (Markdown: https://insights.sbomify.com/CVE-2026-42521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42521
- OSV: https://osv.dev/vulnerability/CVE-2026-42521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42521/
Summaries are generated and may contain mistakes; the official description above is the record.