PT-2026-27419 · Mozilla · Firefox+1

Published 2026-03-24 · Updated 2026-03-24 · CVE-2026-4721

Mitre

Memory safety bugs present in Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird ESR 140.8, Firefox 148 and Thunderbird 148. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, and Firefox ESR < 140.9.

Related Identifiers

CVE-2026-4721

Affected Products

Firefox

Firefox Esr

References · 5

• https://mozilla.org/security/advisories/mfsa2026-21 · Vendor Advisory
• https://mozilla.org/security/advisories/mfsa2026-20 · Vendor Advisory
• https://mozilla.org/security/advisories/mfsa2026-22 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-4721 · Security Note
• https://bugzilla.mozilla.org/buglist.cgi?bug_id=2013762%2C2015291%2C2016591%2C2016661%2C2016664%2C2017303%2C2017894%2C2018090%2C2018196%2C2018379%2C2019112%2C2022090%2C2022243%2C2022351%2C2022478%2C2022676 · Note