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IMMUNITYSEC

CVE-2020-6820

8.1
HIGH
CVSS 3.1
EPSS 7.1% · 94th pctCISA KEV · Exploited in the wild
2020-04-24•Updated 2025-10-21•KEV 2021-11-03
CISA Known Exploited Vulnerabilities

Mozilla Firefox And Thunderbird Use-After-Free Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.

Added to KEV
2021-11-03
Remediation due
2022-05-03

Required action
Apply updates per vendor instructions.

CISA notes
https://nvd.nist.gov/vuln/detail/CVE-2020-6820

Description

Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

Severity

CVSS 3.1 · CISA8.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC · CISA-ADP
Exploitationactive
Automatableno
Technical impacttotal

Affected Products

VendorProductAffected versions
MozillaThunderbird
unspecified to <68.7.0
MozillaFirefox
unspecified to <74.0.1
MozillaFirefox ESR
unspecified to <68.6.1

References

4 Links
Vendor advisories

Record Details

Published
2020-04-24
Last updated
2025-10-21
Assigner (CNA)
mozilla
Credited to
-

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CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.