November 3, 2021 · Applied Cybernetics Group
CVE-2020-6820 — Mozilla Firefox and Thunderbird
Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
- Added to KEV
2021-11-03- Federal due date
2022-05-03- Vendor
- Mozilla
- Product
- Firefox and Thunderbird
- EPSS
- 87.1th percentile (score 0.031, as of
2026-06-08) - NVD CVSS v3.1
- —
- Ransomware use
- Unknown
- Upstream
- https://nvd.nist.gov/vuln/detail/CVE-2020-6820
CISA short description
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.
Required action
Apply updates per vendor instructions.