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CVE-2026-55559

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

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
yamcs / yamcsaffected < 5.12.8; affected >= 5.13.0, < 5.13.2

CWE

CWE-94, CWE-470, CWE-1336

References

ADP enrichment

CISA-ADP

No English description supplied.