CVE-2026-55559

CVSS 9.8 (critical) · published 2026-08-28

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.

Weakness: CWE-94, CWE-470, CWE-1336

Source: NVD CVE-2026-55559

References

• https://github.com/yamcs/yamcs/commit/549f295cf8c5496a5e799d6bec2432ef976c82aa
• https://github.com/yamcs/yamcs/commit/7192da1c49bdf5ab1d72e579a47766a7c43e87c8
• https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8
• https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2
• https://github.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9
• https://github.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9

Check your software

Connect an AI agent to the FixLane MCP server or ask the Telegram bot to check what you have installed against incidents with a verified fixed version.