CVE-2021-1647

HIGHNVD 7.89.0▲
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 7.8 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
7.8
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS: 40%CVSS: 7.8Exploit: NoneExposed: 0

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

Microsoft Defender Remote Code Execution Vulnerability

CVSS v3
7.8
EG Score
9.0(high)
EPSS
98.5%
KEV
⚠ Exploited

Published

January 12, 2021

Last Modified

October 30, 2025

Advisory Details (3)

Auto-updated Jun 4, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: microsoft, 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-2021-1647
microsoft Patch Available

Security Update Guide - Microsoft Security Response Center

Security Update Guide - Microsoft Security Response Center. Patch available via Microsoft Security Update

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1647
microsoft Patch Available

Security Update Guide - Microsoft Security Response Center

Security Update Guide - Microsoft Security Response Center. Patch available via Microsoft Security Update

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1647

Weakness Classification(2)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 93× in last 7d / 390× 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 675 total refreshes for this CVE.

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

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Frequently asked(6)

What is CVE-2021-1647?
CVE-2021-1647 is a high vulnerability published on January 12, 2021. Microsoft Defender Remote Code Execution Vulnerability
When was CVE-2021-1647 disclosed?
CVE-2021-1647 was first published in the National Vulnerability Database on January 12, 2021, with the most recent update on October 30, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-1647 actively exploited?
Yes. CISA added CVE-2021-1647 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Microsoft Defender. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2021-1647?
CVE-2021-1647 has a CVSS v3 base score of 7.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2021-1647?
CVE-2021-1647 affects Microsoft Defender. 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-2021-1647?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-1647, 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-2021-1647

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