CVE-2026-55521

HIGHPre-NVD 8.88.8
EchelonGraph scoreLOW confidence

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: secondary
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs omits authorization checks in IndexesApi.listPacketIndex, IndexesApi.listEventIndex, Cop1Api.disable, Cop1Api.resume, Cop1Api.initialize, Cop1Api.updateConfig, and TimeApi.setTime. An authenticated low-privilege user can read packet and event index metadata without ObjectPrivilegeType.ReadPacket, alter COP-1 link state without SystemPrivilege.ControlLinks, and manipulate simulation time. These operations can disclose telemetry metadata, disrupt telecommand handling, and affect system integrity and availability. This issue is fixed in versions 5.12.8 and 5.13.2.

CVSS v3
8.8
EG Score
8.8(low)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
29%
KEV
Not listed

Published

August 28, 2026

Last Modified

August 28, 2026

Advisory Details (5)

Auto-updated Aug 28, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github Patch Available🟡 PoC Available

Multiple Missing Function Level Access Control vulnerabilities in Yamcs Core API · Advisory · yamcs/yamcs · GitHub

https://github.com/yamcs/yamcs/security/advisories/GHSA-962x-ccwf-8x6p
github_release Patch Available

Yamcs 5.13.2

Patch available: yamcs/yamcs yamcs-5.13.2

https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2
github_release Patch Available

Yamcs 5.12.8

Patch available: yamcs/yamcs yamcs-5.12.8

https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8
github_commit

commit 493563679f83 (yamcs/yamcs)

Fix landed in yamcs/yamcs commit 493563679f83 — awaiting tagged release

https://github.com/yamcs/yamcs/commit/493563679f838b86f3cdc5da9451d4a050ff6bd9
github_commit

commit 405139afa609 (yamcs/yamcs)

Fix landed in yamcs/yamcs commit 405139afa609 — awaiting tagged release

https://github.com/yamcs/yamcs/commit/405139afa6094dfaf63ac17f32df1f808846c950

Vendor Advisories for CVE-2026-55521(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.yamcs:yamcs-core5.13.0, 5.13.15.13.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 3× in last 7d / 3× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-28 20:25 UTCEG score recompute
  3. 2026-08-28 17:11 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55521?
CVE-2026-55521 is a high vulnerability published on August 28, 2026. Yamcs is a mission control framework. Prior to 5.12.8 and 5.13.2, Yamcs omits authorization checks in IndexesApi.listPacketIndex, IndexesApi.listEventIndex, Cop1Api.disable, Cop1Api.resume, Cop1Api.initialize, Cop1Api.updateConfig, and TimeApi.setTime. An authenticated low-privilege user can read…
When was CVE-2026-55521 disclosed?
CVE-2026-55521 was first published in the National Vulnerability Database on August 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55521 actively exploited?
CVE-2026-55521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 71.1% of all scored CVEs.
What is the CVSS score of CVE-2026-55521?
CVE-2026-55521 has a CVSS v3 base score of 8.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-55521?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55521, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-55521

Explore →

Is Your Infrastructure Affected by CVE-2026-55521?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs