CVE-2026-8964

HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-05-19. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, 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.

Spoofing issue in the Popup Blocker component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
22.4%
KEV
Not listed

Published

May 19, 2026

Last Modified

May 20, 2026

Advisory Details (3)

Auto-updated Jun 6, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-50/
generic

Security Vulnerabilities fixed in Firefox 151 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-46/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2025170

Vendor Advisories for CVE-2026-8964(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 40× 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 110 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-8964?
CVE-2026-8964 is a high vulnerability published on May 19, 2026. Spoofing issue in the Popup Blocker component. This vulnerability was fixed in Firefox 151 and Thunderbird 151.
When was CVE-2026-8964 disclosed?
CVE-2026-8964 was first published in the National Vulnerability Database on May 19, 2026, with the most recent update on May 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8964 actively exploited?
CVE-2026-8964 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 22.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-8964?
CVE-2026-8964 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-8964?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8964, 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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