CVE-2026-55559criticalCWE-1336CWE-470CWE-94

CVE-2026-55559: critical vulnerability in yamcs

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

Published

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28Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 9.8epss 0.8%
from disclosure to weapon35 days
Published on NVDAug 28
1st PoC+35d
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Affected products
yamcs · yamcs
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
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