CVE-2021-23995

HIGH

Firefox ESR < 78.10 & Thunderbird < 78.10 - Use After Free

Title source: llm

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.

References (4)

[Issue Tracking, Permissions Required, Vendor Advisory] https://bugzilla.mozilla.org/show_bug.cgi?id=1699835

[Release Notes, 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/

Scores

CVSS v3 8.8

EPSS 0.0103

EPSS Percentile 77.1%

Attack Vector NETWORK

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

Classification

CWE

CWE-672

Status published

Affected Products (3)

mozilla/firefox < 88.0

mozilla/firefox_esr < 78.10

mozilla/thunderbird < 78.10

Timeline

Published Jun 24, 2021

Tracked Since Feb 18, 2026