CVE-2026-82404

HIGHPre-NVD 8.38.3
EchelonGraph scoreMEDIUM confidence

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

Score 8.3 from GitHub Security Advisory (severity: HIGH) published 2026-09-03. A secondary CVSS source baseline 8.3; 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 week

Also known asEUVD-2026-70214 (ENISA EUVD) · GHSA-p95v-992w-h6c3 (GitHub Security Advisories)Source: ENISA EUVD

8.3EG
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).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.7%CVSS: 8.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

TOON is a compact, human-readable serialization of JSON data for LLM prompts. Prior to 2.3.1, decoding attacker-controlled TOON with a __proto__, constructor, or prototype key wrote through the object prototype chain instead of creating an own property, polluting Object.prototype for the runtime. In packages/toon/src/decode/expand.ts, the expandPaths: 'safe' path and insertPathSafe function made dotted keys such as a.__proto__.x the strongest vector, while plain nested objects, tabular rows, quoted keys, and streaming decode were also affected. The encoder also dropped own __proto__ properties and could invoke an inherited setter during normalization. Services that decode untrusted TOON could experience denial of service or, when a suitable downstream gadget is present, remote code execution. This issue is fixed in version 2.3.1.

CVSS v3
8.3
EG Score
8.3HIGHmedium confidence
EG Risk
53
EG Risk 53/100

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)
Severity83% × 45%
Impact severity (EG Severity): CVSS 8.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.7% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
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 none (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
0.7%
EPSS %ILE
52nd
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 (8.3): severity, escalated by confirmed exploitation. This CVE's 8.3 is its impact severity (EG Severity), not escalated.

EG Severity
8.3 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.7% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). 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 none (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 2, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Sep 2, 2026
Patch available. Sources: github, github_pr, github_commit, github_release.
GitHub release Patch Available

v2.3.1

Patch available: toon-format/toon v2.3.1

https://github.com/toon-format/toon/releases/tag/v2.3.1
GitHub commit Patch Available

commit 94a2b7560b2b (toon-format/toon)

Patch available: toon-format/toon v2.3.1 (contains commit 94a2b7560b2b)

https://github.com/toon-format/toon/commit/94a2b7560b2b5ed903a4d466a3bce8b13daa2660
GitHub pull request Patch Available

fix: harden encode and decode against prototype pollution

Patch available: toon-format/toon v2.3.1 (PR #316 merged 2026-07-15)

https://github.com/toon-format/toon/pull/316
GitHub advisoryMentions a patch (unverified)

Prototype pollution when decoding untrusted TOON input · Advisory · toon-format/toon · GitHub

https://github.com/toon-format/toon/security/advisories/GHSA-p95v-992w-h6c3

Vendor Advisories for CVE-2026-82404(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
npm@toon-format/toon @ 2.3.1 (fixes < 2.3.1)—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
@toon-format/toon—
  • every version up to 2.3.1: fixed in 2.3.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 47× 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.

Showing the most recent 98 of 102 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 2 repeat rows among the latest 100 are merged into the row they repeat. The 4 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  2. 2026-11-01 07:38 UTCGHSA enrichmentGHSA-p95v-992w-h6c3 · GitHub severity HIGH · GitHub CVSS 8.3
  3. 2026-11-01 07:38 UTCEG score recompute
  4. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  5. 2026-10-30 16:35 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  6. 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  7. 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  8. 2026-10-27 19:49 UTCEG score recompute
  9. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  10. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  11. 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.7% · 52nd percentile
  12. 2026-10-25 13:58 UTCEG score recompute
  13. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  14. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  15. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  16. 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  17. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  18. 2026-10-20 07:45 UTCEG score recompute
  19. 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  20. 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  21. 2026-10-18 03:08 UTCEG score recompute
  22. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  23. 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  24. 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  25. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.7% · 51st percentile
Show 73 more
  1. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.7% · 51st percentile
  2. 2026-10-13 06:03 UTCEG score recompute
  3. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  4. 2026-10-12 14:55 UTCEG score recompute
  5. 2026-10-11 19:19 UTCEG score recompute
  6. 2026-10-11 16:36 UTCEG score recompute
  7. 2026-10-11 13:54 UTCEG score recompute
  8. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  9. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  10. 2026-10-09 23:47 UTCEG score recompute
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  12. 2026-10-09 01:39 UTCEG score recompute
  13. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  14. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  15. 2026-10-06 19:23 UTCEG score recompute
  16. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  17. 2026-10-06 06:25 UTCEG score recompute
  18. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  19. 2026-10-05 04:28 UTCEG score recompute
  20. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  21. 2026-10-04 02:21 UTCEG score recompute
  22. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  23. 2026-10-03 00:24 UTCEG score recompute
  24. 2026-10-02 17:57 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  25. 2026-10-01 21:21 UTCEG score recompute
  26. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  27. 2026-09-30 19:19 UTCEG score recompute
  28. 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  29. 2026-09-30 03:03 UTCEG score recompute
  30. 2026-09-28 21:59 UTCEG score recompute
  31. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  32. 2026-09-27 20:03 UTCEG score recompute
  33. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  34. 2026-09-26 18:03 UTCEG score recompute
  35. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  36. 2026-09-26 04:52 UTCEG score recompute
  37. 2026-09-25 02:25 UTCEG score recompute
  38. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.7% · 50th percentile
  39. 2026-09-24 00:27 UTCEG score recompute
  40. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  41. 2026-09-22 22:31 UTCEG score recompute
  42. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  43. 2026-09-22 09:31 UTCEG score recompute
  44. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  45. 2026-09-21 07:30 UTCEG score recompute
  46. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  47. 2026-09-19 16:01 UTCEG score recompute
  48. 2026-09-19 02:44 UTCEG score recompute
  49. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  50. 2026-09-18 00:48 UTCEG score recompute
  51. 2026-09-16 22:51 UTCEG score recompute
  52. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  53. 2026-09-16 09:52 UTCEG score recompute
  54. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  55. 2026-09-15 07:22 UTCEG score recompute
  56. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  57. 2026-09-14 04:57 UTCEG score recompute
  58. 2026-09-13 03:01 UTCEG score recompute
  59. 2026-09-12 01:04 UTCEG score recompute
  60. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  61. 2026-09-11 12:05 UTCEG score recompute
  62. 2026-09-10 10:09 UTCEG score recompute
  63. 2026-09-08 23:11 UTCEG score recompute
  64. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  65. 2026-09-07 16:54 UTCEG score recompute
  66. 2026-09-06 14:57 UTCEG score recompute
  67. 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  68. 2026-09-06 01:58 UTCEG score recompute
  69. 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  70. 2026-09-05 00:02 UTCEG score recompute
  71. 2026-09-04 11:04 UTCEG score recompute
  72. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  73. 2026-09-02 19:31 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-82404?
CVE-2026-82404 is a high-severity vulnerability; its CVE record was published on September 2, 2026. TOON is a compact, human-readable serialization of JSON data for LLM prompts. Prior to 2.3.1, decoding attacker-controlled TOON with a proto, constructor, or prototype key wrote through the object prototype chain instead of creating an own property, polluting Object.prototype for the runtime. In…
When was the CVE record for CVE-2026-82404 published?
The CVE record for CVE-2026-82404 was published on September 2, 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 9, 2026; the record at its source may have been updated since.
Is CVE-2026-82404 actively exploited?
CVE-2026-82404 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.7% probability of exploitation in the next 30 days (52nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-82404?
CVE-2026-82404 has a CVSS base score of 8.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-82404?
A fix for CVE-2026-82404 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-82404 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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