Summary
Yamcs's WebSocket subscription handlers omit the privilege checks their REST siblings enforce
Asset / scope: Yamcs 5.12.7 WebSocket topics (packets, algorithm-status, mdb-changes)
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.
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.
Impact
The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.
CVE-2026-55545 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.12.8, 5.13.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
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.
Frequently Asked Questions
- What is CVE-2026-55545? CVE-2026-55545 is a medium-severity missing authorization vulnerability in org.yamcs:yamcs-core (maven), affecting versions <= 5.12.7. It is fixed in 5.12.8, 5.13.2. The application does not perform an authorization check before performing a sensitive operation.
- How severe is CVE-2026-55545? CVE-2026-55545 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.yamcs:yamcs-core are affected by CVE-2026-55545? org.yamcs:yamcs-core (maven) versions <= 5.12.7 is affected.
- Is there a fix for CVE-2026-55545? Yes. CVE-2026-55545 is fixed in 5.12.8, 5.13.2. Upgrade to this version or later.
- Is CVE-2026-55545 exploitable, and should I be worried? Whether CVE-2026-55545 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-55545 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-55545?
- Upgrade
org.yamcs:yamcs-coreto 5.12.8 or later - Upgrade
org.yamcs:yamcs-coreto 5.13.2 or later
- Upgrade