CVE-2026-55545 is a medium-severity (CVSS 6.5) CWE-862 vulnerability in org.yamcs:yamcs-core. O3 Security confirms whether CVE-2026-55545 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Yamcs's WebSocket subscription handlers omit the privilege checks their REST siblings enforce
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 | 5.12.8 |
| ☕Maven | org.yamcs:yamcs-core | ≥ 5.13.0&&< 5.13.2 | 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55545 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55545. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55545 in your dependencies?
O3 detects CVE-2026-55545 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.