CVE-2020-12387

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 1.4%, top 30% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 8.1Exploit: NoneExposed: 0

A fix is available — apply it.

A race condition when running shutdown code for Web Worker led to a use-after-free vulnerability. This resulted in a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
42(Track)
EG Risk 42/100SSVC: 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
Severity81% × 45%
Exploitation1% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
69.7%
KEV
Not listed

Published

May 26, 2020

Last Modified

November 21, 2024

References (14)

Patch Availability(12)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntufirefox-mozsymbols (76.0+build2-0ubuntu0.16.04.1) @ xenial2026-05-27ubuntu
ubuntuxul-ext-lightning (1:68.8.0+build2-0ubuntu0.16.04.2) @ xenial2026-05-27ubuntu
redhatthunderbird-0:68.8.0-1.el7_82020-05-11redhat
redhatthunderbird-0:68.8.0-1.el6_102020-05-11redhat
redhatthunderbird-0:68.8.0-1.el8_22020-05-11redhat
redhatthunderbird-0:68.8.0-1.el8_02020-05-11redhat
redhatthunderbird-0:68.8.0-1.el8_12020-05-11redhat
redhatfirefox-0:68.8.0-1.el6_102020-05-06redhat
redhatfirefox-0:68.8.0-1.el7_82020-05-06redhat
redhatfirefox-0:68.8.0-1.el8_22020-05-06redhat
redhatfirefox-0:68.8.0-1.el8_02020-05-06redhat
redhatfirefox-0:68.8.0-1.el8_12020-05-06redhat

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.

Weakness Classification(2)

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

All Vendor Advisories

(12)

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 14× in last 7d / 43× 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.

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

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Frequently asked(5)

What is CVE-2020-12387?
CVE-2020-12387 is a high vulnerability published on May 26, 2020. A race condition when running shutdown code for Web Worker led to a use-after-free vulnerability. This resulted in a potentially exploitable crash. This vulnerability affects Firefox ESR < 68.8, Firefox < 76, and Thunderbird < 68.8.0.
When was CVE-2020-12387 disclosed?
CVE-2020-12387 was first published in the National Vulnerability Database on May 26, 2020, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-12387 actively exploited?
CVE-2020-12387 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 69.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2020-12387?
CVE-2020-12387 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2020-12387?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-12387, 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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