# CVE-2026-46621: Yamcs: Authenticated Remote Code Execution (RCE) via Jython Algorithm Code Injection

> Authenticated attackers can inject malicious Python code into Yamcs algorithms to execute arbitrary commands on the host system.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** GHSA-2g95-6x5q-xjwj

## What is CVE-2026-46621?

CVE-2026-46621 is a critical code injection vulnerability in yamcs, published on 16 Jul 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Yamcs is a mission control framework. Prior to 5.12.7, the Yamcs script evaluation engine for Python algorithms dynamically compiled and evaluated user-controlled algorithm text using Jython through the JSR-223 ScriptEngine API without enforcing a secure sandbox, so an authenticated user with the ChangeMissionDatabase privilege could override an existing Python algorithm's logic through the mission database REST API and import and execute arbitrary Java classes such as java.lang.Runtime to achieve remote code execution on the underlying host operating system. This issue is fixed in versions 5.12.7 and 5.13.0, which disable algorithm editing by default.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-46621?

2 open source packages ship an affected version, including org.yamcs:yamcs-core. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.yamcs:yamcs-core` | Maven | All versions | 5.12.7 |
| `org.yamcs:yamcs-core` | Maven | All versions | 5.12.7 |

Products: Spaceapplications Yamcs.

## How do I fix CVE-2026-46621?

Upgrade org.yamcs:yamcs-core to 5.12.7 or later.

## Is CVE-2026-46621 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46621 exists.

## Other vulnerabilities in yamcs

- [CVE-2026-46562](https://insights.sbomify.com/CVE-2026-46562/): Yamcs: Remote Code Execution via Mission Database algorithm override (critical 9.8)
- [CVE-2026-44632](https://insights.sbomify.com/CVE-2026-44632/): Yamcs: Server-Side Code Injection (RCE) via Janino Expression Engine in `JavaExprAlgorithmExecutionFactory` (critical 9.1)
- [CVE-2023-45278](https://insights.sbomify.com/CVE-2023-45278/): Yamcs API Directory Traversal vulnerability (critical 9.1)
- [CVE-2023-45277](https://insights.sbomify.com/CVE-2023-45277/): Yamcs Path Traversal vulnerability (high 7.5)
- [CVE-2026-44596](https://insights.sbomify.com/CVE-2026-44596/): Yamcs: No Rate Limiting on Authentication Endpoint (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46621 and fix it if it is affected.

What it is: CVE-2026-46621 is a critical code injection vulnerability in yamcs, published on 16 Jul 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46621 exists.

Affected packages and fixed versions:
- org.yamcs:yamcs-core (Maven): affected all versions; fixed in 5.12.7
- org.yamcs:yamcs-core (Maven): affected all versions; fixed in 5.12.7

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-2026-46621/ (Markdown: https://insights.sbomify.com/CVE-2026-46621/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46621
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46621
- OSV: https://osv.dev/vulnerability/CVE-2026-46621

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46621/
Summaries are generated and may contain mistakes; the official description above is the record.