Valibot helps validate data using a schema. Versions prior to 1.4.2 can throw a TypeError inside its flatten() helper when validation issues contain attacker-controlled object keys such as toString, valueOf, or hasOwnProperty. The issue is reachable through normal record() validation. record() intentionally filters __proto__, prototype, and constructor, but it still accepts other own keys that collide with inherited Object.prototype properties. If the record key schema or value schema rejects such an entry, Valibot creates an issue path containing that key. Passing the resulting issues to Valibot's documented flatten() helper causes flatErrors.nested[dotPath] to resolve to the inherited method instead of an own error array, and the helper calls .push(...) on that function. This is not a global prototype pollution issue. The impact is availability/error handling: applications that validate user-controlled objects with record() and flatten validation errors for API responses can crash the request path with a TypeError instead of returning structured validation errors. This issue has been fixed in version 1.4.2.
CVE-2026-59952
“—” beside the score: it is equal to the CVSS score beside it.
This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (32nd percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2026-50775 (ENISA EUVD) · GHSA-5qjj-4xww-7phc (GitHub Security Advisories)Source: ENISA EUVD
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
A fix is available — apply it.
- CVSS v3
- 6.9
- EG Score
- 6.9MEDIUMmedium confidence
- EG Risk
- 62EG Risk 62/100
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)Severity69% × 45%Impact severity (EG Severity): CVSS 6.9 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
- 0.4%
- EPSS %ILE
- 32nd
- 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 (6.9): severity, escalated by confirmed exploitation. This CVE's 6.9 is its impact severity (EG Severity), not escalated.
- EG Severity
- 6.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 0.4% 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 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
July 24, 2026
Last Modified
October 23, 2026
Advisory Details (4)
Auto-updated Jul 30, 2026v1.4.2
Patch available: open-circle/valibot v1.4.2
https://github.com/open-circle/valibot/releases/tag/v1.4.2commit 1bd01c304657 (open-circle/valibot)
Patch available: open-circle/valibot v1.4.2 (contains commit 1bd01c304657)
https://github.com/open-circle/valibot/commit/1bd01c304657cd0809cc92694360b6cc60f700bffix: handle keys that collide with Object.prototype in flatten and merge
Patch available: open-circle/valibot v1.4.2 (PR #1522 merged 2026-06-28)
https://github.com/open-circle/valibot/pull/1522record() issue paths can make flatten() throw for inherited Object property names · Advisory · open-circle/valibot · GitHub
https://github.com/open-circle/valibot/security/advisories/GHSA-5qjj-4xww-7phcVendor Advisories for CVE-2026-59952(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 / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| npm | valibot @ 1.4.2 (fixes <= 1.4.1) | — | 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)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| valibot | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 42× 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 100 of 151 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. None are among the latest 100 rows. The 51 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-11-01 07:41 UTCGHSA enrichmentGHSA-5qjj-4xww-7phc · GitHub severity MODERATE
- 2026-11-01 07:41 UTCEG score recompute
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-29 16:39 UTCEG score recompute
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
- 2026-10-25 14:16 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-23 22:31 UTCEG score recompute
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-22 20:55 UTCEG score recompute
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-18 03:26 UTCEG score recompute
- 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
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- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-12 15:52 UTCEG score recompute
- 2026-10-11 19:36 UTCEG score recompute
- 2026-10-11 16:51 UTCEG score recompute
- 2026-10-11 14:13 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-04 07:42 UTCEG score recompute
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-03 03:18 UTCEG score recompute
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-10-01 05:59 UTCEG score recompute
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-09-28 04:27 UTCEG score recompute
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
- 2026-09-25 10:07 UTCEG score recompute
- 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 41st percentile
- 2026-09-23 22:17 UTCEG score recompute
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
- 2026-09-22 22:13 UTCEG score recompute
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
- 2026-09-20 01:40 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 23rd percentile
- 2026-09-18 08:39 UTCEG score recompute
- 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-17 10:14 UTCEG score recompute
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-16 11:59 UTCEG score recompute
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-15 09:38 UTCEG score recompute
- 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-14 11:23 UTCEG score recompute
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-13 13:07 UTCEG score recompute
- 2026-09-11 16:36 UTCEG score recompute
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-10 13:36 UTCEG score recompute
- 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-09 08:45 UTCEG score recompute
- 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-06 17:38 UTCEG score recompute
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-05 19:23 UTCEG score recompute
- 2026-09-04 12:51 UTCEG score recompute
- 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-01 23:16 UTCEG score recompute
- 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-30 22:32 UTCEG score recompute
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-30 00:17 UTCEG score recompute
- 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-27 21:06 UTCEG score recompute
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-26 19:52 UTCEG score recompute
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-25 20:59 UTCEG score recompute
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.3% · 22nd percentile
- 2026-08-24 22:43 UTCEG score recompute
- 2026-08-23 02:11 UTCEG score recompute
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
Related CVEs(same product + same CWE)
Frequently asked(5)
What is CVE-2026-59952?
When was the CVE record for CVE-2026-59952 published?
Is CVE-2026-59952 actively exploited?
What is the CVSS score of CVE-2026-59952?
How do I remediate CVE-2026-59952?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-59952
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