Yamcs: Remote Code Execution via instance-template argument YAML injection (createInstance)
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-1336.
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| yamcs | yamcs | before 5.12.8; 5.13.0 to before 5.13.2 | 5.12.8, 5.13.2 | Patch available | CNA |
| — | org.yamcs:yamcs-core (Maven) | 5.13.0 to before 5.13.2 | 5.13.2 | Patch available | GHSA-73mf-m39p-wpm9 |
| — | org.yamcs:yamcs-core (Maven) | before 5.12.8 | 5.12.8 | Patch available | GHSA-73mf-m39p-wpm9 |
- yamcs Vendoryamcs Affected before 5.12.8; 5.13.0 to before 5.13.2 Fixed in 5.12.8, 5.13.2 Patch available CNA
- org.yamcs:yamcs-core (Maven) Vendor— Affected 5.13.0 to before 5.13.2 Fixed in 5.13.2 Patch available GHSA-73mf-m39p-wpm9
- org.yamcs:yamcs-core (Maven) Vendor— Affected before 5.12.8 Fixed in 5.12.8 Patch available GHSA-73mf-m39p-wpm9
Remediation
- Fix · CNA yamcs (yamcs) Fixed in 5.12.8, 5.13.2
- Fix · GHSA-73mf-m39p-wpm9 org.yamcs:yamcs-core (Maven) Fixed in 5.13.2 Advisory →
- Fix · GHSA-73mf-m39p-wpm9 org.yamcs:yamcs-core (Maven) Fixed in 5.12.8 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-55559
- 2026-10-03 Alias added: GHSA-73mf-m39p-wpm9
References
Other 6
- https://github.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9
- 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
More yamcs vulnerabilities
- TI-2026-34240 Yamcs: Remote Code Execution via Mission Database algorithm override CVSS 3.1CRITICAL 9.8
- TI-2026-32507 Yamcs: No Rate Limiting on Authentication Endpoint CVSS 3.1CRITICAL 9.8
- TI-2026-40106 Yamcs: Authenticated remote code execution via unescaped StreamSQL `LIKE` pattern compiled by Janino (`LikeExpression`) CVSS 3.1CRITICAL 9.9
- TI-2026-40057 Yamcs: Authenticated RCE via StreamSQL aggregate-compiler column-name injection in Yamcs `executeSql` CVSS 3.1CRITICAL 9.1
- TI-2026-34277 Yamcs: Authenticated Remote Code Execution (RCE) via Jython Algorithm Code Injection CVSS 3.1CRITICAL 9.1
- TI-2026-32532 Yamcs: Server-Side Code Injection (RCE) via Janino Expression Engine in `JavaExprAlgorithmExecutionFactory` CVSS 3.1CRITICAL 9.1
Sources
- CVE-2026-55559 · CVE Program
- CVE-2026-55559 · NVD
- FIRST EPSS
- GHSA-73mf-m39p-wpm9 · GitHub Advisory Database · CC BY 4.0
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