CVE-2026-61534

CRITICALPre-NVD 9.19.1
EchelonGraph scoreMEDIUM confidence

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

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-09-11. A secondary CVSS source baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-77579 (ENISA EUVD) · GHSA-325j-mg25-8q58 (GitHub Security Advisories)Source: ENISA EUVD

9.1EG
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: 0.8%CVSS: 9.1Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

Yayson is a library for serializing and reading JSON API data in JavaScript. Prior to 4.3.0, Store and LegacyStore use attacker-controlled JSON:API type, id, and relationship names as keys in plain-object lookup tables in src/yayson/store.ts and src/yayson/legacy-store.ts. A document whose type is __proto__ causes model-cache writes to modify Object.prototype, with the attacker controlling the polluted property name through id and its value through attributes. The malicious type can also be supplied by an included resource, and LegacyStore is reachable when a configured types mapping resolves to __proto__. Unsafe relationship names including __proto__, constructor, and prototype provide additional document-derived member paths. The resulting process-wide prototype pollution can cause denial of service and logic corruption; authorization bypass or code execution depends on suitable gadgets in the consuming application. This issue is fixed in version 4.3.0.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
72
EG Risk 72/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity91% × 45%
Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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
0.8%
EPSS %ILE
57th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.

EG Severity
9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.8% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

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 yes (CISA Vulnrichment) · Technical impact partial (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; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (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

September 11, 2026

Last Modified

September 30, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
Patch available. Sources: github_commit, github_pr, github.
GitHub advisoryMentions a patch (unverified)

Prototype pollution in yayson Store/LegacyStore deserialization · Advisory · confetti/yayson · GitHub

https://github.com/confetti/yayson/security/advisories/GHSA-325j-mg25-8q58
GitHub pull request

Prevent prototype pollution attacks in Store and LegacyStore

Fix merged in confetti/yayson PR #111 on 2026-06-22 — awaiting tagged release

https://github.com/confetti/yayson/pull/111
GitHub commit

commit e460162d5a3e (confetti/yayson)

Fix landed in confetti/yayson commit e460162d5a3e — awaiting tagged release

https://github.com/confetti/yayson/commit/e460162d5a3ebac86424bead7424957c36f8dff9

Vendor Advisories for CVE-2026-61534(1)

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

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
npmyayson @ 4.3.0 (fixes <= 4.2.0)—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
yayson—
  • every version up to 4.3.0: fixed in 4.3.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 17× in last 7d / 64× 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. 2026-11-01 23:15 UTCEG score recompute
  2. 2026-11-01 23:15 UTCGHSA enrichmentGHSA-325j-mg25-8q58 · GitHub severity CRITICAL · GitHub CVSS 9.1
  3. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  4. 2026-11-01 07:41 UTCGHSA enrichmentGHSA-325j-mg25-8q58 · GitHub severity CRITICAL · GitHub CVSS 9.1
  5. 2026-11-01 07:41 UTCEG score recompute
  6. 2026-11-01 00:44 UTCEG score recompute
  7. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  8. 2026-10-31 02:12 UTCEG score recompute
  9. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  10. 2026-10-30 03:41 UTCEG score recompute
  11. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  12. 2026-10-29 05:10 UTCEG score recompute
  13. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  14. 2026-10-28 06:40 UTCEG score recompute
  15. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  16. 2026-10-27 08:09 UTCEG score recompute
  17. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  18. 2026-10-26 07:21 UTCEG score recompute
  19. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  20. 2026-10-25 14:14 UTCEG score recompute
  21. 2026-10-25 08:51 UTCEG score recompute
  22. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  23. 2026-10-24 10:20 UTCEG score recompute
  24. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  25. 2026-10-23 11:49 UTCEG score recompute
Show 74 more
  1. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  2. 2026-10-22 13:14 UTCEG score recompute
  3. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  4. 2026-10-21 14:44 UTCEG score recompute
  5. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  6. 2026-10-19 16:54 UTCEG score recompute
  7. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  8. 2026-10-18 18:21 UTCEG score recompute
  9. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  10. 2026-10-18 03:25 UTCEG score recompute
  11. 2026-10-17 19:48 UTCEG score recompute
  12. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  13. 2026-10-16 21:17 UTCEG score recompute
  14. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  15. 2026-10-15 18:13 UTCEG score recompute
  16. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.8% · 57th percentile
  17. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  18. 2026-10-14 11:59 UTCEG score recompute
  19. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  20. 2026-10-13 11:32 UTCEG score recompute
  21. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  22. 2026-10-12 15:50 UTCEG score recompute
  23. 2026-10-11 19:34 UTCEG score recompute
  24. 2026-10-11 16:49 UTCEG score recompute
  25. 2026-10-11 14:11 UTCEG score recompute
  26. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  27. 2026-10-11 11:39 UTCEG score recompute
  28. 2026-10-10 23:06 UTCEG score recompute
  29. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  30. 2026-10-09 20:43 UTCEG score recompute
  31. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  32. 2026-10-08 23:10 UTCEG score recompute
  33. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  34. 2026-10-08 03:53 UTCEG score recompute
  35. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  36. 2026-10-06 18:52 UTCEG score recompute
  37. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  38. 2026-10-05 20:38 UTCEG score recompute
  39. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  40. 2026-10-03 14:48 UTCEG score recompute
  41. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  42. 2026-10-02 18:56 UTCEG score recompute
  43. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  44. 2026-10-01 19:59 UTCEG score recompute
  45. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  46. 2026-09-30 18:09 UTCEG score recompute
  47. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  48. 2026-09-29 16:08 UTCEG score recompute
  49. 2026-09-28 22:58 UTCEG score recompute
  50. 2026-09-28 14:15 UTCEG score recompute
  51. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  52. 2026-09-27 16:49 UTCEG score recompute
  53. 2026-09-26 19:22 UTCEG score recompute
  54. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  55. 2026-09-26 01:46 UTCEG score recompute
  56. 2026-09-24 15:12 UTCEG score recompute
  57. 2026-09-23 22:03 UTCEG score recompute
  58. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  59. 2026-09-22 16:02 UTCEG score recompute
  60. 2026-09-21 22:50 UTCEG score recompute
  61. 2026-09-20 20:53 UTCEG score recompute
  62. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  63. 2026-09-19 18:47 UTCEG score recompute
  64. 2026-09-18 21:20 UTCEG score recompute
  65. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  66. 2026-09-17 19:37 UTCEG score recompute
  67. 2026-09-16 15:43 UTCEG score recompute
  68. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  69. 2026-09-16 07:08 UTCEG score recompute
  70. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  71. 2026-09-14 20:27 UTCEG score recompute
  72. 2026-09-14 19:30 UTCEG score recompute
  73. 2026-09-14 16:26 UTCEG score recompute
  74. 2026-09-11 22:24 UTCEG score recomputeFirst assessed: 9.1 CRITICAL

Frequently asked(5)

What is CVE-2026-61534?
CVE-2026-61534 is a critical-severity vulnerability; its CVE record was published on September 11, 2026. Yayson is a library for serializing and reading JSON API data in JavaScript. Prior to 4.3.0, Store and LegacyStore use attacker-controlled JSON:API type, id, and relationship names as keys in plain-object lookup tables in src/yayson/store.ts and src/yayson/legacy-store.ts. A document whose type is…
When was the CVE record for CVE-2026-61534 published?
The CVE record for CVE-2026-61534 was published on September 11, 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 30, 2026; the record at its source may have been updated since.
Is CVE-2026-61534 actively exploited?
CVE-2026-61534 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.8% probability of exploitation in the next 30 days (57th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-61534?
CVE-2026-61534 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-61534?
A fix for CVE-2026-61534 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-61534 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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