PT-2026-30822 · Mozilla · Firefox+1

Published 2026-04-07 · Updated 2026-04-07 · CVE-2026-5731

NVD

CVSS v3.1

9.8

Critical

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

Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 < 149.0.2, Firefox ESR < 115.34.1, and Firefox ESR < 140.9.1.

Fix

Buffer Overflow

Weakness Enumeration

CWE-119

Related Identifiers

CVE-2026-5731

Affected Products

Firefox

Firefox Esr

References · 5

• https://mozilla.org/security/advisories/mfsa2026-27 · Vendor Advisory
• https://mozilla.org/security/advisories/mfsa2026-25 · Vendor Advisory
• https://mozilla.org/security/advisories/mfsa2026-26 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-5731 · Security Note
• https://bugzilla.mozilla.org/buglist.cgi?bug_id=2021894%2C2022225%2C2022252%2C2022294%2C2023007%2C2023130%2C2023191%2C2023364%2C2023829%2C2024074%2C2024417%2C2024433%2C2024436%2C2024437%2C2024453%2C2024461%2C2024462%2C2024472%2C2024474%2C2024477%2C2025364%2C2025401%2C2025402%2C2025472%2C2026287%2C2026299%2C2026305%2C2026426 · Note