SEPTEMBER 15, 2026
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Case File

CVE-2026-55559

CRITICAL · CVSS 9.8 EPSS 0.55% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-08-28 · Last synced 2026-09-15

CyberRota Analysis

AI-Generated

Yamcs versions prior to 5.12.8 and 5.13.2 are vulnerable to a critical command injection flaw due to improper handling of template arguments in YAML configuration, which allows attackers to inject malicious service entries. This vulnerability can lead to remote code execution as the Yamcs service account, particularly affecting deployments lacking a security.yaml file or those requiring elevated privileges. Organizations using affected versions of Yamcs should prioritize immediate updates to mitigate this severe risk.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-55559
Severity
CRITICAL
CVSS
9.8
EPSS
0.55%
Java

Original 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.