Answer in brief
CVE-2026-55559 records a Critical severity (CVSS 9.8) vulnerability in Yamcs: Remote Code Execution via instance-template argument YAML injection (createInstance). The current sources do not mark it as known exploited. The current feed maps org.yamcs:yamcs-core (maven), org.yamcs:yamcs-core (maven). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps org.yamcs:yamcs-core (maven), org.yamcs:yamcs-core (maven). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| org.yamcs:yamcs-coremaven | >=5.13.0,<=5.13.1 | 5.13.2 |
| org.yamcs:yamcs-coremaven | <=5.12.7 | 5.12.8 |
Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 28, 2026
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.
Quoted source text, attributed separately from HOL analysis.