CVE-2020-6820
Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
Mozilla · Firefox and Thunderbird
Vulnerability details
Mozilla Firefox and Thunderbird contain a race condition vulnerability when handling a ReadableStream under certain conditions. The race condition creates a use-after-free vulnerability, causing unspecified impacts.
Added to CISA KEV: 2021-11-03
Ransomware campaign use: Unknown
CISA due date: 2022-05-03
Defensive guidance from CISA
Apply updates per vendor instructions.
This is the source's required-action field, not an independently validated patch procedure. Refer to the vendor for exact affected versions and fixes.
Source catalog date: 2026-11-06T19:44:45.1797Z · Last retrieved: 2026-11-06 21:02:26 UTC