Mozilla Firefox and Thunderbird
YES - ON THE CISA KEV LIST
CVE-2020-6819
Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
overdue since 2022-05-03
Mozilla: 13 entries (0.7% of all KEV entries are from this vendor); 0 added in 2026.
BOD 26-04 note: this is the date printed in the CISA catalog. A federal agency's actual deadline is set by its SSVC tier - Act (3 days), Attend (14 days), Track (60 days), or the next scheduled upgrade - counted from the KEV listing date or the date the vulnerability is identified in its environment, whichever comes first. Use the tier helper on each CVE page for your own window.
Your BOD 26-04 window (SSVC tier helper)
Your remediation window ends:
Description
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.
Required action (CISA)
Apply updates per vendor instructions.
Notes
https://nvd.nist.gov/vuln/detail/CVE-2020-6819
References
Other KEV entries for this vendor: Mozilla
- CVE-2010-3765 - Multiple Products (2025-10-06)
- CVE-2024-9680 - Firefox (2024-10-15)
- CVE-2016-9079 - Firefox, Firefox ESR, and Thunderbird (2023-06-22)
- CVE-2015-4495 - Firefox (2022-05-25)
- CVE-2019-11707 - Firefox and Thunderbird (2022-05-23)
- CVE-2019-11708 - Firefox and Thunderbird (2022-05-23)
- CVE-2013-1690 - Firefox and Thunderbird (2022-03-28)
- CVE-2022-26486 - Firefox (2022-03-07)
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