---
title: "CVE-2026-46621: Yamcs Vulnerable to Authenticated Remote Code Execution (RCE) via Jython Algorithm Code Injection"
url: https://erroneo.us/security/cve/CVE-2026-46621/
description: "CVE-2026-46621 (org.yamcs:yamcs-core (Maven)): Yamcs is a mission control framework. Prior to 5.12.7, the Yamcs script evaluation engine for Python…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-16
date_modified: 2026-07-16
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-46621"
kev: false
cvss: 9.1
epss: 0.01116
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.1% , percentile 66: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 66% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (high (admin)). Exposure depends on who can log in.
- Only applies if your dependency tree includes org.yamcs:yamcs-core (Maven) < 5.12.7, fixed in 5.12.7 . Check your lockfile, including transitive dependencies.

## What it is

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.

## Affected packages

- Maven `org.yamcs:yamcs-core` < 5.12.7 → fixed: 5.12.7

## Affected products (CVE record)

- yamcs yamcs: < 5.12.7

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.12% probability of exploitation activity in the next 30 days; percentile 66.

## Sources

- [GitHub Advisory GHSA-2g95-6x5q-xjwj](https://github.com/advisories/GHSA-2g95-6x5q-xjwj)
- [CVE.org record CVE-2026-46621](https://www.cve.org/CVERecord?id=CVE-2026-46621)
- [NVD entry CVE-2026-46621](https://nvd.nist.gov/vuln/detail/CVE-2026-46621)
- [github.com](https://github.com/yamcs/yamcs/security/advisories/GHSA-2g95-6x5q-xjwj)
- [github.com](https://github.com/yamcs/yamcs/commit/3c550348f866af4675d2ba4a51d8d12b7c7c6011)
- [github.com](https://github.com/yamcs/yamcs/commit/4ff8fda642ea8c3309a4d3f379aa77b763148992)
- [github.com](https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.7)
- [github.com](https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.0)

---
Source page: https://erroneo.us/security/cve/CVE-2026-46621/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt