CVE-2026-55545 is a medium-severity (CVSS 6.5) CWE-862 vulnerability in org.yamcs:yamcs-core. A fix is available for org.yamcs:yamcs-core — see the affected versions and patch details below.
Yamcs: WebSocket subscription handlers omit the privilege checks their REST siblings enforce
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55545.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55545 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.yamcs:yamcs-core☕org.yamcs:yamcs-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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 noReadPacketcheck, while the REST siblings do (listPackets:128,streamPackets:256,subscribeContainers:538). A principal with a narrowReadPacketscope receives the raw binary of all TM packets on the processor.algorithm-status(ProcessingApi.subscribeAlgorithmStatus) performs no check, while RESTgetAlgorithmStatusenforcescheckObjectPrivileges(ReadAlgorithm, ...)(:467).mdb-changes(MdbOverrideApi.subscribeMdbChanges) performs no check, while base MDB reads requireGetMissionDatabase.
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.
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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 security policy. We might publish a write-up after a fix and the agreed window.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.yamcs:yamcs-core | all versions | 5.12.8org.yamcs:yamcs-core:5.12.8 |
| ☕Maven | org.yamcs:yamcs-core | ≥ 5.13.0&&< 5.13.2 | 5.13.2org.yamcs:yamcs-core:5.13.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.yamcs:yamcs-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.yamcs:yamcs-core to 5.12.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55545 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-55545 in your dependencies?
Find it across Maven, including transitive dependencies.