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Advisory record · GHSA-73mf-m39p-wpm9

Yamcs vulnerable to Remote Code Execution via instance-template argument YAML injection (createInstance)

CVSS 9.8 CriticalCriticalEPSS 0.0078 · 56th percentile

Critical, because:

  • CVSS score 9.8: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 28 Aug 2026, 17:23 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
org.yamcs:yamcs-coreMaven>=5.13.0, <5.13.2 || <5.12.85.13.2, 5.12.8
Identifiers
GHSA-73mf-m39p-wpm9 · CVE-2026-55559
Weakness (CWE)
CWE-94 · CWE-470 · CWE-1336
Tags
Published
28 Aug 2026
Updated
28 Aug 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Yamcs versions from 5.13.0 before 5.13.2 and before 5.12.8 are vulnerable to remote code execution through the templateArgs field of the instance creation and update API, because values are written into the instance config as unescaped YAML. An attacker with the CreateInstances privilege, or any unauthenticated user on a server without a security.yaml file, can inject a service that runs an arbitrary command as the Yamcs service account. Upgrade to Yamcs 5.13.2 or 5.12.8. Until then, require authentication and withhold CreateInstances from users who should not have shell access.

Written 2 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.8 Critical 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0078, the 56th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:19 UTC First seen by agentprime
  2. 31 Oct 2026, 14:19 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.