Yamcs Core API has Multiple Missing Function Level Access Control vulnerabilities

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-55521: 0.52% estimated exploitation activity in the next 30 days; percentile 44.44 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Multiple Missing Function Level Access Control vulnerabilities exist in the Yamcs Core API. These vulnerabilities allow any authenticated user, regardless of their assigned roles or privileges (e.g., an unprivileged "Guest"), to bypass intended access controls. An attacker can exploit these flaws to extract sensitive telemetry metadata, disrupt satellite communication link protocols (COP-1), and manipulate the global simulation time, severely impacting the confidentiality, integrity, and availability of the system. Details Yamcs utilizes a robust Role-Based Access Control (RBAC) model with SystemPrivilege and ObjectPrivilege to restrict administrative actions and data retrieval. However, three critical API controllers completely omit these authorization checks before executing internal business logic: 1. IndexesApi.java (Information Disclosure): Unlike PacketsApi.java, which filters results using ctx.user.hasObjectPrivilege(ObjectPrivilegeType.ReadPacket, packetName), methods…

Published by the source

28 Aug 2026, 17:09 UTC

Last modified by the source

28 Aug 2026, 17:25 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-962x-ccwf-8x6p

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-962x-ccwf-8x6p

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# Patch Next advisory brief: CVE-2026-55521

Advisory: Yamcs Core API has Multiple Missing Function Level Access Control vulnerabilities
IDs: CVE-2026-55521, GHSA-962x-ccwf-8x6p
Record: https://patchnext.com/advisories/cve-2026-55521 (revision 2, source checked 26 Oct 2026, 16:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.yamcs:yamcs-core 5.13.2, 5.12.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.yamcs:yamcs-core: affected >= 5.13.0, <= 5.13.1; <= 5.12.7; fixed in 5.12.8, 5.13.2

## Suggested inspection (read-only)
- Maven org.yamcs:yamcs-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.yamcs:yamcs-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-962x-ccwf-8x6p (OSV record GHSA-962x-ccwf-8x6p lists affected ranges: Maven org.yamcs:yamcs-core >=5.13.0 =0 <5.12.8 (fixed))
- Verified: https://github.com/advisories/GHSA-962x-ccwf-8x6p (GitHub-reviewed advisory GHSA-962x-ccwf-8x6p lists affected ranges: Maven org.yamcs:yamcs-core >=5.13.0 =0 <=5.12.7)

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