CVE-2026-64909

HIGHPre-NVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-08-11. the CNA's CVSS baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:microsoft, epss, ghsa
Trending — 4 sources updated this week
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: None knownExposed: 0

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

Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
35(Track)
EG Risk 35/100SSVC: Track

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
Severity78% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 11, 2026

Last Modified

September 16, 2026

Advisory Details (1)

Auto-updated Aug 11, 2026
Patch available. Sources: microsoft.
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-2026-64909

Vendor Advisories for CVE-2026-64909(2)

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

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 37× in last 7d / 188× 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 313 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-64909?
CVE-2026-64909 is a high vulnerability published on August 11, 2026. Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.
When was CVE-2026-64909 disclosed?
CVE-2026-64909 was first published in the National Vulnerability Database on August 11, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-64909 actively exploited?
CVE-2026-64909 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 72.4% of all scored CVEs.
What is the CVSS score of CVE-2026-64909?
CVE-2026-64909 has a CVSS v4.0 base score of 7.8 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-64909?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-64909, 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

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