CVE-2026-55559
Yamcs: Remote Code Execution via instance-template argument YAML injection (createInstance)
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Awaiting Analysis | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.78% · top 44% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: yes · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Weakness
- CWE-94: Improper Control of Generation of Code ('Code Injection') (opens in a new tab)All about CWE-94 and its CVEs
- CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') (opens in a new tab)All about CWE-470 and its CVEs
- CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine (opens in a new tab)All about CWE-1336 and its CVEs
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Mavenorg.yamcs:yamcs-coreGHSA-73mf-m39p-wpm9 (opens in a new tab)
References (5)
- https://github.com/yamcs/yamcs/security/advisories/GHSA-73mf-m39p-wpm9 (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/yamcs/yamcs/commit/549f295cf8c5496a5e799d6bec2432ef976c82aa (opens in a new tab)x_refsource_MISC
- https://github.com/yamcs/yamcs/commit/7192da1c49bdf5ab1d72e579a47766a7c43e87c8 (opens in a new tab)x_refsource_MISC
- https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8 (opens in a new tab)x_refsource_MISC
- https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-73mf-m39p-wpm9 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-55559)Record last updated .