CVE-2020-6820

criticalknown exploitedcovered by 1 sourcefirst seen 2021-11-03

Actively exploited. CVE-2020-6820 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03) — exploitation has been observed in the wild, and US federal agencies are required to remediate it under BOD 22-01. Treat patching as urgent.

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.

CSIRTS triage

What: Mozilla Firefox and Thunderbird contain a race condition vulnerability leading to a use-after-free condition.
Who is affected: Users of Mozilla Firefox and Thunderbird.
Urgency: Remediation is urgent due to active exploitation and critical severity.
Action: Update to the latest versions of Firefox and Thunderbird.

AI-assisted analysis generated from the source advisory — verify against the original.

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Exploitation outlook

Exploitation confirmedAlready exploited in the wild (CISA KEV) — the prediction phase is over. Patch now. Riskier than 93% of all EPSS-scored CVEs.

Advisory coverage (1)

criticalexploitedCVE-2020-6820: Mozilla Firefox And Thunderbird Use-After-Free Vulnerabilitycisa-kev · 2021-11-03

External references

NVD record for CVE-2020-6820

CVE.org record

CISA KEV catalog

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