CVE-2026-55559

9.8 CRITICAL 0.8% exploit odds Fix listed Injection

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 0.8% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-06-16 23:11 UTC ReservedThe CVE id was reserved by its CNA
2026-08-28 20:18 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-08 21:08 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.8% in the next 30 days (EPSS).
Severity: 9.8 CRITICAL (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-08-28 20:18 UTC
Last modified: 2026-09-08 21:08 UTC
Exploit probability: 0.8% · EPSS, next 30 days
Weakness: CWE-94 · Code injection
Record status: Awaiting Analysis

Attack profile CVSS 3.1 · 9.8

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-55559.md and follow it. Check whether this project is affected by CVE-2026-55559. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record