CVE-2026-55521

HIGHPre-NVD 8.88.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (42nd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated
8.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 8.8Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
8.8HIGHmedium confidence
EG Risk
56
EG Risk 56/100

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 (value × EchelonGraph’s weight)
Severity88% × 45%
The EG Score, 8.8 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.5%
EPSS %ILE
42nd
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low, Track* at medium and Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 28, 2026

Last Modified

September 8, 2026

Advisory Details (5)

Auto-updated Aug 28, 2026
Patch available. Sources: github_commit, github_release, github.
GitHub advisoryMentions a patch (unverified)

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 rangeFix by version rangeDependents
org.yamcs:yamcs-core0.29.3 ... 5.9.9 (166 versions)
  • 5.13.0 up to 5.13.2: fixed in 5.13.2
  • every version up to 5.12.8: fixed in 5.12.8
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 57× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  3. 2026-10-12 15:41 UTCEG score recompute
  4. 2026-10-11 19:39 UTCEG score recompute
  5. 2026-10-11 16:54 UTCEG score recompute
  6. 2026-10-11 14:17 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  9. 2026-10-10 00:50 UTCEG score recompute
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-09 02:39 UTCEG score recompute
  12. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  13. 2026-10-08 00:51 UTCEG score recompute
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-10-06 22:44 UTCEG score recompute
  16. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  17. 2026-10-06 00:48 UTCEG score recompute
  18. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  19. 2026-10-05 01:20 UTCEG score recompute
  20. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  21. 2026-10-03 16:02 UTCEG score recompute
  22. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  23. 2026-10-03 04:48 UTCEG score recompute
  24. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  25. 2026-10-02 06:47 UTCEG score recompute
Show 60 more
  1. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  2. 2026-09-30 19:49 UTCEG score recompute
  3. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  4. 2026-09-30 03:49 UTCEG score recompute
  5. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  6. 2026-09-29 02:45 UTCEG score recompute
  7. 2026-09-28 15:47 UTCEG score recompute
  8. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  9. 2026-09-27 17:41 UTCEG score recompute
  10. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-09-26 19:19 UTCEG score recompute
  12. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  13. 2026-09-26 08:04 UTCEG score recompute
  14. 2026-09-24 18:42 UTCEG score recompute
  15. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  16. 2026-09-23 19:52 UTCEG score recompute
  17. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  18. 2026-09-22 21:40 UTCEG score recompute
  19. 2026-09-21 23:36 UTCEG score recompute
  20. 2026-09-21 01:40 UTCEG score recompute
  21. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  22. 2026-09-19 16:42 UTCEG score recompute
  23. 2026-09-19 05:44 UTCEG score recompute
  24. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  25. 2026-09-17 20:50 UTCEG score recompute
  26. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  27. 2026-09-16 18:58 UTCEG score recompute
  28. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  29. 2026-09-16 05:25 UTCEG score recompute
  30. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  31. 2026-09-15 06:44 UTCEG score recompute
  32. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  33. 2026-09-13 21:51 UTCEG score recompute
  34. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  35. 2026-09-12 23:55 UTCEG score recompute
  36. 2026-09-11 15:01 UTCEG score recompute
  37. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  38. 2026-09-10 17:04 UTCEG score recompute
  39. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  40. 2026-09-09 08:09 UTCEG score recompute
  41. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  42. 2026-09-08 02:01 UTCEG score recompute
  43. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  44. 2026-09-06 16:10 UTCEG score recompute
  45. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  46. 2026-09-05 18:12 UTCEG score recompute
  47. 2026-09-04 20:11 UTCEG score recompute
  48. 2026-09-04 09:10 UTCEG score recompute
  49. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  50. 2026-09-03 00:00 UTCEG score recompute
  51. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  52. 2026-09-01 15:04 UTCEG score recompute
  53. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  54. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  55. 2026-08-31 05:38 UTCEG score recompute
  56. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  57. 2026-08-30 07:42 UTCEG score recompute
  58. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  59. 2026-08-28 20:25 UTCEG score recompute
  60. 2026-08-28 17:11 UTCEG score recomputeFirst assessed: 8.8 HIGH

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-55521?
CVE-2026-55521 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55521 published?
The CVE record for CVE-2026-55521 was published on August 28, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 8, 2026; the record at its source may have been updated since.
Is CVE-2026-55521 actively exploited?
CVE-2026-55521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (42nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55521?
CVE-2026-55521 has a CVSS base score of 8.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55521?
A fix for CVE-2026-55521 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55521 are linked in the Vendor Advisories panel on this page.

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