CVE-2020-6819

CRITICALNVD 8.19.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 8.1 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 5 sources updated this weekExploited in the wild
9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 3%CVSS: 8.1Exploit: cisa kev · ssvc activeExposed: 0

A fix is available — apply it.

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

CVSS v3
8.1
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: Attend

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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
3%
EPSS %ILE
86%
KEV
⚠ Exploited

Published

April 24, 2020

Last Modified

November 4, 2025

Advisory Details (4)

Auto-updated Jun 3, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-6819
generic

Security Vulnerabilities fixed in Thunderbird 68.7.0 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2020-14/
generic🔴 Active Exploitation

Security Vulnerabilities fixed in Firefox 74.0.1 and Firefox ESR 68.6.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2020-11/
generic🔴 Active Exploitation

1620818 - (CVE-2020-6819) AddressSanitizer: heap-use-after-free /builds/worker/workspace/build/src/docshell/base/nsDocShell.cpp:3302:12 in SynchronizeLayoutHistoryState

https://bugzilla.mozilla.org/show_bug.cgi?id=1620818

Patch Availability(11)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuxul-ext-lightning (1:68.7.0+build1-0ubuntu0.18.04.1) @ bionic2026-07-28ubuntu
ubuntuxul-ext-lightning (1:68.7.0+build1-0ubuntu0.16.04.2) @ xenial2026-07-28ubuntu
ubuntufirefox-mozsymbols (74.0.1+build1-0ubuntu0.16.04.1) @ xenial2026-07-28ubuntu
redhatthunderbird-0:68.7.0-1.el8_02020-04-16redhat
redhatthunderbird-0:68.7.0-1.el8_12020-04-16redhat
redhatthunderbird-0:68.7.0-1.el6_102020-04-16redhat
redhatthunderbird-0:68.7.0-1.el7_82020-04-16redhat
redhatfirefox-0:68.6.1-1.el6_102020-04-07redhat
redhatfirefox-0:68.6.1-1.el8_12020-04-07redhat
redhatfirefox-0:68.6.1-1.el8_02020-04-07redhat
redhatfirefox-0:68.6.1-1.el7_82020-04-07redhat

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(3)

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

All Vendor Advisories

(11)

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 65× in last 7d / 398× 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 815 total refreshes for this CVE.

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

Frequently asked(6)

What is CVE-2020-6819?
CVE-2020-6819 is a critical vulnerability published on April 24, 2020. Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.
When was CVE-2020-6819 disclosed?
CVE-2020-6819 was first published in the National Vulnerability Database on April 24, 2020, with the most recent update on November 4, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-6819 actively exploited?
Yes. CISA added CVE-2020-6819 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Mozilla Firefox and Thunderbird. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2020-6819?
CVE-2020-6819 has a CVSS v3 base score of 8.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2020-6819?
CVE-2020-6819 affects Mozilla Firefox and Thunderbird. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2020-6819?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-6819, 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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