Is CVE-2020-6819 actively exploited?

Yes. KEV Intelligence tracks CVE-2020-6819 as a known exploited vulnerability. Confidence is confirmed.

What exploitation activity has KEV Intelligence observed?

KEV Intelligence has not yet recorded sensor-observed exploitation attempts for CVE-2020-6819. Our sensors continue to monitor for activity targeting this CVE.

Which versions are affected?

CVE-2020-6819 affects Mozilla Thunderbird and 2 other products. Reported affected versions include unspecified to < 68.7.0, unspecified to < 74.0.1, and unspecified to < 68.6.1.

Yes. CVE-2020-6819 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2020-6819

Q: How should organizations remediate it?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Q: Is it in CISA KEV?

Yes. CVE-2020-6819 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Thunderbird

Mozilla / Thunderbird · affected before 68.7.0

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Severity: CVSS 8.1 · High
Confidence: Confirmed
Exploit status: Exploited in the wild
EPSS: 3.0%
First observed: —
Last observed: —

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2020-6819 is an unauthenticated vulnerability affecting Mozilla Thunderbird and 2 other products. Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We...

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Mozilla / Thunderbird affected before 68.7.0.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free

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.

Vendor Product Affected Status

Mozilla Thunderbird Before 68.7.0 Affected

Mozilla Firefox Before 74.0.1 Affected

Mozilla Firefox ESR Before 68.6.1 Affected

View vendor advisory

Published: 24 Apr 2020
Exploitation Reported: 03 Nov 2021
Attack vector: Remote
Complexity: High
Privileges: None
User interaction: None

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2020-6819
USN-4335-1 usn.ubuntu.com · Vendor Advisory https://usn.ubuntu.com/4335-1/
mozilla.org/security/advisories/mfsa2020-14 mozilla.org · CVE Record https://www.mozilla.org/security/advisories/mfsa2020-14/
mozilla.org/security/advisories/mfsa2020-11 mozilla.org · CVE Record https://www.mozilla.org/security/advisories/mfsa2020-11/
bugzilla.mozilla.org/show_bug.cgi bugzilla.mozilla.org · CVE Record https://bugzilla.mozilla.org/show_bug.cgi?id=1620818

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 03 Nov 2021

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source	Added
CISA First	2021-11-03 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets: 0
User-Agents: 0

Raw values available in Pro and Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.1 High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

3.0%

Weaknesses

Use After Free CWE-416

All CVSS Scores

CVSS v3.1 8.1 High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0 6.8 Medium

AV:N/AC:M/Au:N/C:P/I:P/A:P

Timeline

From disclosure to observed exploitation

03 Nov 2021
Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
24 Apr 2020
CVE published

Vulnerability disclosed publicly
10 Jan 2020
CVE ID reserved

Identifier reserved by the CNA

Pro API

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Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2020-6819

Free JSON includes basic KEV fields

{
  "cve_id": "CVE-2020-6819",
  "confidence": "Confirmed",
  "cvss_score": 8.1,
  "cvss_estimated": false,
  "epss_score": 0.02978,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

Early warning alerts

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