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CVE-2026-55559

9.8 · CRITICAL

Yamcs is a mission control framework.

Published Aug 28, 2026CWE-94EPSS 0.78%

Overview

CVE-2026-55559 is a critical-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs inserts templateArgs from POST /api/instances and PATCH /api/instances/{instance} into YAML through VarStatement.append in yamcs-core/src/main/java/org/yamcs/templating/VarStatement.java without YAML-context escaping. The rendered configuration is parsed by YamcsServer.createInstance and loaded by YamcsServerInstance, allowing an attacker to inject a services entry for org.yamcs.ProcessRunner. Deployments without security.yaml expose the operation through the guest superuser, while secured deployments require SystemPrivilege.CreateInstances. Successful exploitation executes commands as the Yamcs service account. This issue is fixed in versions 5.12.8 and 5.13.2.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/yamcs/yamcs/commit/549f295cf8c5496a5e799d6bec2432ef976c82aaGitHubgithub.com/yamcs/yamcs/commit/7192da1c49bdf5ab1d72e579a47766a7c43e87c8GitHubgithub.com/yamcs/yamcs/releases/tag/yamcs-5.12.8GitHubgithub.com/yamcs/yamcs/releases/tag/yamcs-5.13.2GitHubgithub.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9GitHubgithub.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9

How CyberStrike helps

Frequently asked questions

What is CVE-2026-55559?

CVE-2026-55559 is a critical-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-55559?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-55559?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-55559?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-55559 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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