Back to Database
Status published
High
CVE-2021-23960
Performing garbage collection on re-declared JavaScript variables resulted in a...
Vulnerability 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.
Impact Analysis
Refer to official advisory for detailed impact metrics.
Remediation
Ensure systems are updated to the latest vendor-supplied patch levels.
THREAT MONITOR
Am I Vulnerable?
Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2021-23960
Credits & Attribution
No credits recorded in the NVD database.
References
More from Mozilla
View All →CVE-2025-9187
Memory safety bugs fixed in Firefox 142 and Thunderbird 142
Unknown
0
CVE-2025-9186
Spoofing issue in the Address Bar component of Firefox Focus for Android
Unknown
0
CVE-2025-9185
Memory safety bugs fixed in Firefox ESR 115.27, Firefox ESR 128.14, Thunderbird ESR 128.14, Firefox ESR 140.2, Thunderbird ESR 140.2, Firefox 142 and Thunderbird 142
Unknown
0
CVE-2025-9184
Memory safety bugs fixed in Firefox ESR 140.2, Thunderbird ESR 140.2, Firefox 142 and Thunderbird 142
Unknown
0
CVE-2025-9183
Spoofing issue in the Address Bar component
Unknown
0
Affected Vendor
Mozilla
View all reports →Affected Software
Firefox, Thunderbird, Firefox ESR
Vulnerable Versions:
< 85, < 78.7
Timeline
Official Publish:
February 26th, 2021
Last Modified:
August 3rd, 2024
Added to House:
July 21st, 2026
CVSS Vectors
V3:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weaknesses (CWE)
No CWE data available
MITRE ATT&CK TTPs
No associated TTPs found for this vulnerability.