CVE-2021-23960

HIGH

Firefox <85, Thunderbird <78.7, Firefox ESR <78.7 - Use After Free

Title source: llm
STIX 2.1

Description

Performing garbage collection on re-declared JavaScript variables resulted in a user-after-poison, and a potentially exploitable crash. This vulnerability affects Firefox < 85, Thunderbird < 78.7, and Firefox ESR < 78.7.

References (4)

Core 4
Core References
Release Notes, Vendor Advisory x_refsource_misc
https://www.mozilla.org/security/advisories/mfsa2021-03/
Release Notes, Vendor Advisory x_refsource_misc
https://www.mozilla.org/security/advisories/mfsa2021-04/
Release Notes, Vendor Advisory x_refsource_misc
https://www.mozilla.org/security/advisories/mfsa2021-05/
Issue Tracking, Permissions Required, Vendor Advisory x_refsource_misc
https://bugzilla.mozilla.org/show_bug.cgi?id=1675755

Scores

CVSS v3 8.8
EPSS 0.0030
EPSS Percentile 53.7%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Details

Status published
Products (3)
mozilla/firefox < 85.0
mozilla/firefox_esr < 78.7
mozilla/thunderbird < 78.7
Published Feb 26, 2021
Tracked Since Feb 18, 2026