CVE-2021-30666

HIGHNVD 8.89.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 8.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 5 sources updated this weekExploited in the wild
8.8
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 3%CVSS: 8.8Exploit: NoneExposed: 0

A fix is available — apply it.

A buffer overflow issue was addressed with improved memory handling. This issue is fixed in iOS 12.5.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..

CVSS v3
8.8
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: 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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS
86.1%
KEV
⚠ Exploited

Published

September 8, 2021

Last Modified

October 23, 2025

Advisory Details (2)

Auto-updated Jun 2, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30666
generic🔴 Active Exploitation

About the security content of iOS 12.5.3 - Apple Support

https://support.apple.com/en-us/HT212341

Vendor Advisories for CVE-2021-30666(3)

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

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatwebkitgtk4-0:2.48.3-2.el7_92025-07-07redhat
redhatwebkit2gtk3-0:2.28.4-1.el82020-11-04redhat
redhatwebkitgtk4-0:2.28.2-2.el72020-09-29redhat

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.

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 106× in last 7d / 421× 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.

Showing the most recent 100 of 749 total refreshes for this CVE.

  1. 2026-07-23 02:00 UTCEG score recompute
  2. 2026-07-23 00:21 UTCEG score recompute
  3. 2026-07-23 00:21 UTCVendor advisory
  4. 2026-07-23 00:21 UTCGHSA enrichment
  5. 2026-07-22 22:47 UTCEG score recompute
  6. 2026-07-22 20:18 UTCVendor advisory
  7. 2026-07-22 20:18 UTCGHSA enrichment
  8. 2026-07-22 19:40 UTCCISA KEV update
  9. 2026-07-22 16:14 UTCEG score recompute
  10. 2026-07-22 16:14 UTCVendor advisory
  11. 2026-07-22 16:14 UTCGHSA enrichment
  12. 2026-07-22 14:06 UTCEPSS rescore
  13. 2026-07-22 14:06 UTCEPSS rescore
  14. 2026-07-22 12:08 UTCVendor advisory
  15. 2026-07-22 12:08 UTCGHSA enrichment
  16. 2026-07-22 08:05 UTCVendor advisory
  17. 2026-07-22 08:05 UTCGHSA enrichment
  18. 2026-07-22 04:03 UTCVendor advisory
  19. 2026-07-22 04:03 UTCGHSA enrichment
  20. 2026-07-21 23:59 UTCVendor advisory
  21. 2026-07-21 23:59 UTCGHSA enrichment
  22. 2026-07-21 18:17 UTCEG score recompute
  23. 2026-07-21 18:17 UTCVendor advisory
  24. 2026-07-21 18:17 UTCGHSA enrichment
  25. 2026-07-21 15:22 UTCEPSS rescore
Show 75 more
  1. 2026-07-21 15:22 UTCEPSS rescore
  2. 2026-07-21 14:37 UTCCISA KEV update
  3. 2026-07-21 14:13 UTCVendor advisory
  4. 2026-07-21 14:13 UTCGHSA enrichment
  5. 2026-07-21 10:11 UTCVendor advisory
  6. 2026-07-21 10:10 UTCGHSA enrichment
  7. 2026-07-21 06:07 UTCVendor advisory
  8. 2026-07-21 06:07 UTCGHSA enrichment
  9. 2026-07-21 02:04 UTCVendor advisory
  10. 2026-07-21 02:04 UTCGHSA enrichment
  11. 2026-07-20 22:00 UTCVendor advisory
  12. 2026-07-20 22:00 UTCGHSA enrichment
  13. 2026-07-20 17:57 UTCEG score recompute
  14. 2026-07-20 17:57 UTCVendor advisory
  15. 2026-07-20 17:57 UTCGHSA enrichment
  16. 2026-07-20 17:05 UTCEPSS rescore
  17. 2026-07-20 13:53 UTCVendor advisory
  18. 2026-07-20 13:53 UTCGHSA enrichment
  19. 2026-07-20 09:50 UTCVendor advisory
  20. 2026-07-20 09:50 UTCGHSA enrichment
  21. 2026-07-20 05:47 UTCVendor advisory
  22. 2026-07-20 05:47 UTCGHSA enrichment
  23. 2026-07-20 01:44 UTCVendor advisory
  24. 2026-07-20 01:44 UTCGHSA enrichment
  25. 2026-07-19 21:41 UTCVendor advisory
  26. 2026-07-19 21:41 UTCGHSA enrichment
  27. 2026-07-19 17:38 UTCEG score recompute
  28. 2026-07-19 17:38 UTCVendor advisory
  29. 2026-07-19 17:38 UTCGHSA enrichment
  30. 2026-07-19 14:28 UTCEPSS rescore
  31. 2026-07-19 13:35 UTCVendor advisory
  32. 2026-07-19 13:35 UTCGHSA enrichment
  33. 2026-07-19 09:33 UTCVendor advisory
  34. 2026-07-19 09:33 UTCGHSA enrichment
  35. 2026-07-19 05:30 UTCEG score recompute
  36. 2026-07-19 05:30 UTCVendor advisory
  37. 2026-07-19 05:30 UTCGHSA enrichment
  38. 2026-07-19 02:27 UTCEPSS rescore
  39. 2026-07-19 02:27 UTCEPSS rescore
  40. 2026-07-19 01:27 UTCVendor advisory
  41. 2026-07-19 01:27 UTCGHSA enrichment
  42. 2026-07-18 21:25 UTCVendor advisory
  43. 2026-07-18 21:25 UTCGHSA enrichment
  44. 2026-07-18 17:22 UTCVendor advisory
  45. 2026-07-18 17:22 UTCGHSA enrichment
  46. 2026-07-18 13:19 UTCEG score recompute
  47. 2026-07-18 13:19 UTCVendor advisory
  48. 2026-07-18 13:19 UTCGHSA enrichment
  49. 2026-07-18 10:02 UTCEPSS rescore
  50. 2026-07-18 10:02 UTCEPSS rescore
  51. 2026-07-18 09:16 UTCVendor advisory
  52. 2026-07-18 09:16 UTCGHSA enrichment
  53. 2026-07-18 05:13 UTCVendor advisory
  54. 2026-07-18 05:13 UTCGHSA enrichment
  55. 2026-07-18 01:10 UTCVendor advisory
  56. 2026-07-18 01:10 UTCGHSA enrichment
  57. 2026-07-17 21:07 UTCVendor advisory
  58. 2026-07-17 21:07 UTCGHSA enrichment
  59. 2026-07-17 17:04 UTCVendor advisory
  60. 2026-07-17 17:04 UTCGHSA enrichment
  61. 2026-07-17 13:02 UTCVendor advisory
  62. 2026-07-17 13:02 UTCGHSA enrichment
  63. 2026-07-17 08:58 UTCEG score recompute
  64. 2026-07-17 08:58 UTCVendor advisory
  65. 2026-07-17 08:58 UTCGHSA enrichment
  66. 2026-07-17 04:55 UTCVendor advisory
  67. 2026-07-17 04:55 UTCGHSA enrichment
  68. 2026-07-17 00:52 UTCVendor advisory
  69. 2026-07-17 00:52 UTCGHSA enrichment
  70. 2026-07-16 20:49 UTCVendor advisory
  71. 2026-07-16 20:49 UTCGHSA enrichment
  72. 2026-07-16 17:04 UTCCISA KEV update
  73. 2026-07-16 17:00 UTCEPSS rescore
  74. 2026-07-16 16:46 UTCVendor advisory
  75. 2026-07-16 16:45 UTCGHSA enrichment

Related CVEs(same vendor + same CWE)

Frequently asked(6)

What is CVE-2021-30666?
CVE-2021-30666 is a high vulnerability published on September 8, 2021. A buffer overflow issue was addressed with improved memory handling. This issue is fixed in iOS 12.5.3. Processing maliciously crafted web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited..
When was CVE-2021-30666 disclosed?
CVE-2021-30666 was first published in the National Vulnerability Database on September 8, 2021, with the most recent update on October 23, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-30666 actively exploited?
Yes. CISA added CVE-2021-30666 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Apple iOS. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-30666?
CVE-2021-30666 has a CVSS v3 base score of 8.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-30666?
CVE-2021-30666 affects Apple iOS. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2021-30666?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-30666, 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

Explore the affected products and dependency analysis for CVE-2021-30666

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