CVE-2026-55559

Summary

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 Software

VendorProductVersion RangeStatus
yamcsyamcs< 5.12.8affected
yamcsyamcs>= 5.13.0, < 5.13.2affected

Weaknesses

  • CWE-94: CWE-94: Improper Control of Generation of Code ('Code Injection')
  • CWE-470: CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')
  • CWE-1336: CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: yes
    • Technical Impact: total

Additional References

References