CVE-2026-84637

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-09-02. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 3 sources updated this week
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0

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

Malicious calendar invitations could use file URI attachments to launch local or network-hosted executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new invitation display enabled, the attachment could also appear under a misleading filename. This vulnerability was fixed in Thunderbird 154 and Thunderbird 153.2.

CVSS v3
9.8
EG Score
9.8(high)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity98% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

September 1, 2026

Last Modified

September 3, 2026

Advisory Details (3)

Auto-updated Sep 17, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 153.2 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-88/
generic

Security Vulnerabilities fixed in Thunderbird 154 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-78/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2043878

Vendor Advisories for CVE-2026-84637(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 53× in last 7d / 144× 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 144 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-84637?
CVE-2026-84637 is a critical vulnerability published on September 1, 2026. Malicious calendar invitations could use file URI attachments to launch local or network-hosted executables on Windows, bypassing Thunderbird's normal executable attachment protections. With the new invitation display enabled, the attachment could also appear under a misleading filename. This…
When was CVE-2026-84637 disclosed?
CVE-2026-84637 was first published in the National Vulnerability Database on September 1, 2026, with the most recent update on September 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-84637 actively exploited?
CVE-2026-84637 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 72.5% of all scored CVEs.
What is the CVSS score of CVE-2026-84637?
CVE-2026-84637 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-84637?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-84637, 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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