CVE-2026-59952

MEDIUMPre-NVD 6.96.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 78% of all CVEs by exploit prediction. 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: epss, secondary
Elevated
6.9EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.9Exploit: Elevated riskExposed: 0

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

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.

CVSS v3
6.9
EG Score
6.9(medium)
EG Risk
62(Attend)
EG Risk 62/100SSVC: Attend

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
Severity69% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
0%
EPSS %ILE
22%
KEV
Not listed

Published

July 24, 2026

Last Modified

July 30, 2026

Advisory Details (4)

Auto-updated Jul 30, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github, github_pr, github_commit.
github_release Patch Available

v1.4.2

Patch available: open-circle/valibot v1.4.2

https://github.com/open-circle/valibot/releases/tag/v1.4.2
github_commit Patch Available

commit 1bd01c304657 (open-circle/valibot)

Patch available: open-circle/valibot v1.4.2 (contains commit 1bd01c304657)

https://github.com/open-circle/valibot/commit/1bd01c304657cd0809cc92694360b6cc60f700bf
github_pr Patch Available

fix: 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/1522
github Patch Available🟡 PoC Available

record() 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-7phc

Vendor 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.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
valibot—1.4.2—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 55× 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. 2026-08-25 20:59 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 22:43 UTCEG score recompute
  4. 2026-08-23 02:11 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 03:55 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 05:39 UTCEG score recompute
  9. 2026-08-20 22:55 UTCEPSS rescore
  10. 2026-08-20 07:24 UTCEG score recompute
  11. 2026-08-19 17:04 UTCEPSS rescore
  12. 2026-08-19 09:07 UTCEG score recompute
  13. 2026-08-18 13:48 UTCEPSS rescore
  14. 2026-08-18 10:49 UTCEG score recompute
  15. 2026-08-17 13:47 UTCEPSS rescore
  16. 2026-08-17 12:33 UTCEG score recompute
  17. 2026-08-16 14:56 UTCEPSS rescore
  18. 2026-08-16 14:17 UTCEG score recompute
  19. 2026-08-16 02:14 UTCEPSS rescore
  20. 2026-08-15 16:02 UTCEG score recompute
  21. 2026-08-15 01:30 UTCEPSS rescore
  22. 2026-08-14 17:46 UTCEG score recompute
  23. 2026-08-13 22:00 UTCEPSS rescore
  24. 2026-08-12 21:11 UTCEG score recompute
  25. 2026-08-12 13:51 UTCEPSS rescore
Show 31 more
  1. 2026-08-11 22:47 UTCEG score recompute
  2. 2026-08-11 00:26 UTCEG score recompute
  3. 2026-08-11 00:00 UTCEPSS rescore
  4. 2026-08-10 02:11 UTCEG score recompute
  5. 2026-08-09 13:46 UTCEPSS rescore
  6. 2026-08-09 03:56 UTCEG score recompute
  7. 2026-08-08 16:37 UTCEPSS rescore
  8. 2026-08-08 05:41 UTCEG score recompute
  9. 2026-08-07 07:26 UTCEG score recompute
  10. 2026-08-06 13:47 UTCEPSS rescore
  11. 2026-08-06 09:10 UTCEG score recompute
  12. 2026-08-05 19:17 UTCEPSS rescore
  13. 2026-08-05 10:55 UTCEG score recompute
  14. 2026-08-04 15:10 UTCEPSS rescore
  15. 2026-08-04 12:39 UTCEG score recompute
  16. 2026-08-04 10:39 UTCEPSS rescore
  17. 2026-08-03 13:21 UTCEG score recompute
  18. 2026-08-03 10:36 UTCEPSS rescore
  19. 2026-08-02 15:05 UTCEG score recompute
  20. 2026-08-02 02:27 UTCEPSS rescore
  21. 2026-08-01 16:50 UTCEG score recompute
  22. 2026-08-01 04:16 UTCEPSS rescore
  23. 2026-07-30 20:14 UTCEG score recompute
  24. 2026-07-30 16:28 UTCEPSS rescore
  25. 2026-07-30 15:38 UTCEG score recompute
  26. 2026-07-30 15:00 UTCEG score recompute
  27. 2026-07-30 01:38 UTCEG score recompute
  28. 2026-07-30 01:03 UTCEG score recompute▲ 6.90
  29. 2026-07-30 00:52 UTCMITRE cvelistV5CVSS v3 → 6.9 · CVSS v4 → 6.9
  30. 2026-07-27 23:55 UTCEG score recompute
  31. 2026-07-24 17:13 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-59952?
CVE-2026-59952 is a medium vulnerability published on July 24, 2026. 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()…
When was CVE-2026-59952 disclosed?
CVE-2026-59952 was first published in the National Vulnerability Database on July 24, 2026, with the most recent update on July 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59952 actively exploited?
CVE-2026-59952 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 77.8% of all scored CVEs.
What is the CVSS score of CVE-2026-59952?
CVE-2026-59952 has a CVSS v3 base score of 6.9 (NVD).
How do I remediate CVE-2026-59952?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59952, 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-2026-59952

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