CVE-2021-23995

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.

• CWE-672

• 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

Published

Jun 24, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-23988Mozilla developers reported memory safety bugs present in Fi…8.8
• CVE-2021-2399Vulnerability in the MySQL Server product of Oracle MySQL (c…4.9
• CVE-2021-23991If a Thunderbird user has previously imported Alice's OpenPG…6.8
• CVE-2021-23992Thunderbird did not check if the user ID associated with an …4.3
• CVE-2021-23993An attacker may perform a DoS attack to prevent a user from …6.5
• CVE-2021-23994A WebGL framebuffer was not initialized early enough, result…8.8
• CVE-2021-23996By utilizing 3D CSS in conjunction with Javascript, content …6.5
• CVE-2021-23997Due to unexpected data type conversions, a use-after-free co…8.8
• CVE-2021-23998Through complicated navigations with new windows, an HTTP pa…6.5
• CVE-2021-23999If a Blob URL was loaded through some unusual user interacti…8.8
• CVE-2021-2400Vulnerability in the Oracle BI Publisher product of Oracle F…7.5
• CVE-2021-24000A race condition with requestPointerLock() and setTimeout() …3.1