fkie_cve-2026-55545

Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs WebSocket subscription handlers fail to enforce the privileges required by equivalent REST endpoints. PacketsApi.subscribePackets exposes the packets WebSocket topic without ObjectPrivilegeType.ReadPacket, ProcessingApi.subscribeAlgorithmStatus exposes the algorithm-status WebSocket topic without ObjectPrivilegeType.ReadAlgorithm, and MdbOverrideApi.subscribeMdbChanges exposes the mdb-changes WebSocket topic without SystemPrivilege.GetMissionDatabase. A low-privilege authenticated user can receive telemetry packets, algorithm status, and mission database change information outside the assigned authorization scope. This issue is fixed in versions 5.12.8 and 5.13.2.

GHSA-fwww-cp23-7f5g — Yamcs's WebSocket subscription handlers omit the privilege checks their REST siblings enforce

Affected: Maven: org.yamcs:yamcs-core

**Asset / scope:** Yamcs 5.12.7 WebSocket topics (`packets`, `algorithm-status`, `mdb-changes`)

## Summary

Several WebSocket subscription handlers do not perform the privilege check that their REST counterparts enforce, so a principal subscribing over WebSocket receives data the REST API would have scoped or denied.

## Root cause

- `packets` (`PacketsApi.subscribePackets`) performs no `ReadPacket` check, while the REST siblings do (`listPackets:128`, `streamPackets:256`, `subscribeContainers:538`). A principal with a narrow `ReadPacket` scope receives the raw binary of all TM packets on the processor. - `algorithm-status` (`ProcessingApi.subscribeAlgorithmStatus`) performs no check, while REST `getAlgorithmStatus` enforces `checkObjectPrivileges(ReadAlgorithm, ...)` (`:467`). - `mdb-changes` (`MdbOverrideApi.subscribeMdbChanges`) performs no check, while base MDB reads require `GetMissionDatabase`.

## Remediation

Bring each WebSocket subscription handler to parity with its REST sibling's privilege check (`ReadPacket`, `ReadAlgorithm`, `GetMissionDatabase`). This is the same declarative fail-closed fix as Report 1.

## Supporting material

Subsystem source audit of the WS-vs-REST authorization parity. Available on request.

## Disclosure and credit

This was found by Cipher / Causal Security - https://causalsecurity.com/. We are coordinating disclosure via this report and request CVEs where you agree they qualify. We propose the 90-day window stated in your…

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fkie_cve-2026-55545

GHSA-fwww-cp23-7f5g — Yamcs's WebSocket subscription handlers omit the privilege checks their REST siblings enforce