CVE-2026-35209

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.0%, top 95% 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, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

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

defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to defu() are vulnerable to prototype pollution. A crafted payload containing a __proto__ key can override intended default values in the merged resul. The internal _defu function used Object.assign({}, defaults) to copy the defaults object. Object.assign invokes the __proto__ setter, which replaces the resulting object's [[Prototype]] with attacker-controlled values. Properties inherited from the polluted prototype then bypass the existing __proto__ key guard in the for...in loop and land in the final result. Version 6.1.5 replaces Object.assign({}, defaults) with object spread ({ ...defaults }), which uses [[DefineOwnProperty]] and does not invoke the __proto__ setter.

CVSS v3
7.5
EG Score
7.5(medium)
EPSS
31.9%
KEV
Not listed

Published

April 6, 2026

Last Modified

April 27, 2026

Advisory Details (4)

Auto-updated Jun 11, 2026
Patch available. Sources: github_commit, github_pr, github_release, github.
github Patch Available

Prototype pollution via `__proto__` key in defaults argument · Advisory · unjs/defu · GitHub

https://github.com/unjs/defu/security/advisories/GHSA-737v-mqg7-c878
github_release Patch Available

v6.1.5

Patch available: unjs/defu v6.1.5

https://github.com/unjs/defu/releases/tag/v6.1.5
github_pr Patch Available

fix: prevent prototype pollution via `__proto__`

Patch available: unjs/defu v6.1.5 (PR #156 merged 2026-04-01)

https://github.com/unjs/defu/pull/156
github_commit Patch Available

commit 3942bfbbcaa7 (unjs/defu)

Patch available: unjs/defu v6.1.5 (contains commit 3942bfbbcaa7)

https://github.com/unjs/defu/commit/3942bfbbcaa72084bd4284846c83bd61ed7c8b29

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
defu—6.1.5—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 41× 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. 2026-07-12 05:46 UTCEPSS rescore
  2. 2026-07-11 08:27 UTCEPSS rescore
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-08 15:15 UTCEPSS rescore
  5. 2026-07-07 13:46 UTCEPSS rescore
  6. 2026-07-06 16:27 UTCEPSS rescore
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  8. 2026-07-06 02:23 UTCEPSS rescore
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  10. 2026-07-05 02:30 UTCEPSS rescore
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-01 15:06 UTCEPSS rescore
  13. 2026-06-30 23:22 UTCEPSS rescore
  14. 2026-06-29 14:06 UTCEPSS rescore
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  16. 2026-06-28 14:07 UTCEPSS rescore
  17. 2026-06-28 14:07 UTCEPSS rescore
  18. 2026-06-28 04:56 UTCEPSS rescore
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  20. 2026-06-27 03:08 UTCEPSS rescore
  21. 2026-06-25 13:49 UTCEPSS rescore
  22. 2026-06-25 13:49 UTCEPSS rescore
  23. 2026-06-24 14:05 UTCEPSS rescore
  24. 2026-06-23 21:33 UTCEPSS rescore
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  1. 2026-06-22 14:25 UTCEPSS rescore
  2. 2026-06-22 14:25 UTCEPSS rescore
  3. 2026-06-21 14:56 UTCEPSS rescore
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  5. 2026-06-21 01:59 UTCEPSS rescore
  6. 2026-06-19 19:25 UTCEPSS rescore
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  8. 2026-06-18 17:52 UTCEPSS rescore
  9. 2026-06-18 17:52 UTCEPSS rescore
  10. 2026-06-17 17:53 UTCEPSS rescore
  11. 2026-06-16 17:52 UTCEPSS rescore
  12. 2026-06-15 17:49 UTCEPSS rescore
  13. 2026-06-14 23:18 UTCEPSS rescore
  14. 2026-06-13 23:00 UTCEPSS rescore
  15. 2026-06-12 23:12 UTCEPSS rescore
  16. 2026-06-12 23:12 UTCEPSS rescore
  17. 2026-06-11 21:34 UTCEG score recompute
  18. 2026-06-11 14:00 UTCEPSS rescore
  19. 2026-06-10 22:18 UTCEPSS rescore
  20. 2026-06-10 13:22 UTCEPSS rescore
  21. 2026-06-10 13:01 UTCEG score recompute
  22. 2026-06-10 01:13 UTCEG score recompute
  23. 2026-06-09 14:04 UTCEG score recompute
  24. 2026-06-08 14:17 UTCEPSS rescore
  25. 2026-06-08 14:17 UTCEPSS rescore
  26. 2026-06-08 08:38 UTCEG score recompute
  27. 2026-06-07 21:34 UTCEG score recompute
  28. 2026-06-07 15:25 UTCEPSS rescore
  29. 2026-06-07 15:25 UTCEPSS rescore
  30. 2026-06-07 15:25 UTCEPSS rescore
  31. 2026-06-07 10:29 UTCEG score recompute
  32. 2026-06-06 13:47 UTCEPSS rescore
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  34. 2026-06-05 22:47 UTCEPSS rescore
  35. 2026-06-05 22:47 UTCEPSS rescore
  36. 2026-06-05 06:10 UTCEPSS rescore
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  38. 2026-06-04 13:12 UTCEPSS rescore
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  40. 2026-06-02 20:13 UTCEPSS rescore
  41. 2026-06-01 13:52 UTCEPSS rescore
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  43. 2026-06-01 13:51 UTCEPSS rescore
  44. 2026-05-31 22:30 UTCEPSS rescore
  45. 2026-05-31 22:30 UTCEPSS rescore
  46. 2026-05-31 00:16 UTCEPSS rescore
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  48. 2026-05-31 00:16 UTCEPSS rescore
  49. 2026-05-29 13:44 UTCEPSS rescore
  50. 2026-05-29 13:44 UTCEPSS rescore
  51. 2026-05-28 13:44 UTCEPSS rescore
  52. 2026-05-28 13:44 UTCEPSS rescore
  53. 2026-05-28 13:44 UTCEPSS rescore
  54. 2026-05-27 13:40 UTCEPSS rescore
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  57. 2026-05-26 13:44 UTCEPSS rescore
  58. 2026-05-26 07:18 UTCEPSS rescore
  59. 2026-05-26 07:18 UTCEPSS rescore
  60. 2026-05-23 00:08 UTCEG score recompute
  61. 2026-05-20 22:38 UTCEPSS rescore
  62. 2026-05-20 22:38 UTCEPSS rescore
  63. 2026-05-20 18:51 UTCEG score recompute
  64. 2026-05-20 11:22 UTCEPSS rescore
  65. 2026-05-20 11:22 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-35209?
CVE-2026-35209 is a high vulnerability published on April 6, 2026. defu is software that allows uers to assign default properties recursively. Prior to version 6.1.5, applications that pass unsanitized user input (e.g. parsed JSON request bodies, database records, or config files from untrusted sources) as the first argument to defu() are vulnerable to prototype…
When was CVE-2026-35209 disclosed?
CVE-2026-35209 was first published in the National Vulnerability Database on April 6, 2026, with the most recent update on April 27, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-35209 actively exploited?
CVE-2026-35209 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 31.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-35209?
CVE-2026-35209 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-35209?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-35209, 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.

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