CVE-2026-55521 Yamcs : Multiple Missing Function Level Access Control vulnerabilities in Yamcs Core API
Low-privilege users can access telemetry metadata and disrupt telecommand handling due to missing authorization checks in Yamcs Core API.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55521?
CVE-2026-55521 is a high-severity missing authorization vulnerability in yamcs, published on 28 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs omits authorization checks in IndexesApi.listPacketIndex, IndexesApi.listEventIndex, Cop1Api.disable, Cop1Api.resume, Cop1Api.initialize, Cop1Api.updateConfig, and TimeApi.setTime. An authenticated low-privilege user can read packet and event index metadata without ObjectPrivilegeType.ReadPacket, alter COP-1 link state without SystemPrivilege.ControlLinks, and manipulate simulation time. These operations can disclose telemetry metadata, disrupt telecommand handling, and affect system integrity and availability. This issue is fixed in versions 5.12.8 and 5.13.2.
Weakness: CWE-862
Which versions are affected by CVE-2026-55521?
4 open source packages ship an affected version, including org.yamcs:yamcs-core.
| Package | Affected | Fixed in |
|---|---|---|
org.yamcs:yamcs-core Maven | All versions | 5.12.8 |
org.yamcs:yamcs-core Maven | All versions | 5.12.8 |
org.yamcs:yamcs-core Maven | From 5.13.0 | 5.13.2 |
org.yamcs:yamcs-core Maven | From 5.13.0 | 5.13.2 |
How do I fix CVE-2026-55521?
Upgrade org.yamcs:yamcs-core to a fixed version for your release line: 5.12.8 or 5.13.2.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-55521 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55521 exists.
Sources
Also known as GHSA-962x-ccwf-8x6p.