CVE-2021-23960

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.

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

Published

Feb 26, 2021

Last Modified

Jun 17, 2026

Status

Modified

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