CVE-2021-23995
Mozilla: Use-after-free in Responsive Design Mode
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Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · April 19, 2021
Updated · November 22, 2025
Description
When Responsive Design Mode was enabled, it used references to objects that were previously freed. We presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 8.8CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE-416 · Use After Free