CVE-2020-6820
Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
IN CISA KEV
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.
- Vendor
- Mozilla
- Product
- Firefox and Thunderbird
- CVSS
- No score recorded (no NVD record loaded for this entry)
- CWE
- CWE-362
- Published
- Not recorded
- NVD modified
- Not recorded
CISA KEV
- Date added
- 2021-11-03
- Due date
- 2022-05-03
- Ransomware use
- Unknown
- Required action
- Apply updates per vendor instructions.
EPSS
7.06% chance of exploitation in the next 30 days (percentile 94th)
FIRST EPSS, updated 17 Oct 2026. About EPSS
CVSS is severity, EPSS is likelihood, KEV means already exploited. EPSS is a statistical probability, not a certainty: a low score does not make a bug safe, and a high one does not prove it is being exploited.
Data last updated 18 Oct 2026. Sources: NVD API 2.0, CISA KEV catalog, FIRST EPSS. Links: NVD, CISA KEV. Metadata only. ThreatWire does not host exploit code.