CVE-2021-23995

HighCVSS 8.8/10Last modified Jun 17, 2026

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.

Metrics

CVSS 3.1 8.8/10CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-672

Affected software

Vendor	Product	Versions
Mozilla	Firefox ESR	>= unspecified, < 78.10
Mozilla	Thunderbird	>= unspecified, < 78.10
Mozilla	Firefox	>= unspecified, < 88

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1699835Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1699835Issue Tracking, Permissions Required, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-14/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-15/Release Notes, Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-16/Release Notes, Vendor Advisory

Timeline

Published: Jun 24, 2021
Last modified: Jun 17, 2026
NVD status: Modified

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