CVE-2026-74987

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-18. 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 — 4 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: 1%CVSS: 9.8Exploit: None knownExposed: 0

A fix is available — apply it.

Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.

CVSS v3
9.8
EG Score
9.8(medium)
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%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

August 18, 2026

Last Modified

September 1, 2026

Advisory Details (9)

Auto-updated Sep 16, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 153.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-80/
generic

Security Vulnerabilities fixed in Thunderbird 140.14 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-79/
generic

Security Vulnerabilities fixed in Thunderbird 154 — Mozilla

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

Security Vulnerabilities fixed in Firefox ESR 153.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-77/
generic

Security Vulnerabilities fixed in Firefox ESR 140.14 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-76/
generic

Security Vulnerabilities fixed in Firefox 154 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-74/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2059424
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667
generic

Client Challenge

https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645

Vendor Advisories for CVE-2026-74987(16)

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

Patch Availability(21)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatthunderbird-0:140.14.0-1.el9_22026-09-09redhat
redhatthunderbird-0:140.14.0-1.el8_42026-09-09redhat
redhatfirefox-0:140.14.0-1.el9_22026-09-09redhat
redhatthunderbird-0:140.14.0-1.el8_62026-09-09redhat
redhatthunderbird-0:140.14.0-1.el8_82026-09-09redhat
redhatfirefox-0:140.14.0-1.el8_82026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_62026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_62026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_22026-09-08redhat
redhatthunderbird-0:140.14.0-1.el10_02026-09-08redhat
redhatthunderbird-0:140.14.0-1.el8_102026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_82026-09-08redhat
redhatfirefox-0:140.14.0-1.el9_42026-09-08redhat
redhatthunderbird-0:140.14.0-1.el9_42026-09-08redhat
redhatfirefox-0:140.14.0-1.el9_62026-09-08redhat
redhatfirefox-0:140.14.0-1.el10_02026-09-08redhat
redhatfirefox-0:140.14.0-1.el7_92026-09-08redhat
redhatfirefox-0:140.14.0-1.el8_42026-09-08redhat
redhatfirefox-0:140.14.0-1.el9_82026-08-24redhat
redhatfirefox-0:140.14.0-1.el8_102026-08-24redhat
redhatfirefox-0:140.14.0-1.el10_22026-08-24redhat

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.

Affected Packages

(6 across 3 ecosystems)
Debian:12(2)
PackageVulnerable rangeFixed inDependents
firefox-esr102.11.0esr-1 ... 140.9.1esr-1~deb13u1 (195 versions)140.14.0esr-1~deb12u1—
thunderbird1:102.11.0-1 ... 1:140.9.1esr-1~deb13u1 (224 versions)1:140.14.0esr-1~deb12u1—
Debian:13(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (71 versions)140.14.0esr-1~deb13u1—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (80 versions)1:140.14.0esr-1~deb13u1—
Debian:14(2)
PackageVulnerable rangeFixed inDependents
firefox-esr128.13.0esr-1 ... 140.9.1esr-1~deb13u1 (72 versions)140.14.0esr-2—
thunderbird1:128.13.0esr-1 ... 1:140.9.1esr-1~deb13u1 (81 versions)1:140.14.0esr-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(6)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 79× in last 7d / 337× 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 355 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-74987?
CVE-2026-74987 is a critical vulnerability published on August 18, 2026. Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was…
When was CVE-2026-74987 disclosed?
CVE-2026-74987 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on September 1, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-74987 actively exploited?
CVE-2026-74987 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 56.7% of all scored CVEs.
What is the CVSS score of CVE-2026-74987?
CVE-2026-74987 has a CVSS v3.1 base score of 9.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-74987?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-74987, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-74987

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