CVE-2020-6819 — Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
Overview
Mozilla Firefox and Thunderbird contain a race condition vulnerability when running the nsDocShell destructor under certain conditions. The race condition creates a use-after-free vulnerability, causing unspecified impacts.
Vulnerability details
- CVE ID
- CVE-2020-6819
- Vulnerability
- Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
- Vendor
- Mozilla
- Affected products
- Mozilla: Firefox and Thunderbird
- Severity
- HIGH
- Exploitation status
- Actively exploited in the wild (CISA KEV)
- Published
- 2021-11-03
Remediation guidance
CVE-2020-6819 is in CISA's Known Exploited Vulnerabilities (KEV) catalog — U.S. federal civilian agencies are required to remediate it under Binding Operational Directive 22-01. Treat it as a priority for every environment.
Apply the vendor's official security update for Mozilla the affected product as soon as possible. Where a patch is unavailable, apply vendor mitigations or isolate/segment exposed systems.
Hunt for indicators of compromise tied to this vulnerability and confirm logging/EDR coverage on affected assets.
Authoritative references
Remediate CVE-2020-6819 — and stay ahead of the next one
CVE-2020-6819 is listed in the CISA KEV catalog as actively exploited — treat remediation as urgent. Scan your domain free to see whether CVE-2020-6819 and other Mozilla issues affect you and get a prioritized remediation report (full report from ₹999) — or stream the full feed of 1,600+ actively-exploited CVEs straight into your SOC.
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