CVSS 3.1
9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVE-2026-55559
Critical (9.8). EPSS 0.8% chance of exploitation in the next 30 days. Fixed in org.yamcs:yamcs-core 5.12.8, 5.13.2.
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.
Severity
- EPSS
- 0.8% chance of exploitation in the next 30 days; higher than 56% of CVEs (scores of 2026-10-31)
- CWEs
- CWE-94, CWE-470, CWE-1336
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-73mf-m39p-wpm9 | Maven | org.yamcs:yamcs-core | >=5.13.0 <5.13.2 | 5.13.2 |
| GHSA-73mf-m39p-wpm9 | Maven | org.yamcs:yamcs-core | <5.12.8 | 5.12.8 |
References
- 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