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CVE-2020-6820: Mozilla Firefox And Thunderbird Use-After-Free Vulnerability

criticalknown exploitedCVE-2020-6820
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation 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

vendor: Mozillaproduct: Firefox and ThunderbirdOther
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.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2021-11-03
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2020-6820

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2020-6820coverage & exploitation statusNVD · CVE.org

Recent advisories for Mozilla Firefox And

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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