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Vulnerability record · CVE-2026-55559 · published 28 August 2026

CVE-2026-55559: Code injection vulnerability

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.

9.8 CVSS 3.1 Critical EPSS 0.78% · top 45.7% CWE-94 · Code injectionCWE-470 · CWE-470 Awaiting Analysis
9.8CVSS 3.1 base score
0.78%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
6References
8 Sep 2026Last modified by NVD

Description

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

References

LinkTags
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

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Source: NIST National Vulnerability Database (record CVE-2026-55559), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.