CVE-2026-4720
Critical · CVSS 9.8Mozilla Firefox / Firefox ESR / Thunderbird — Memory safety bugs / Buffer overflow leading to arbitrary code execution (CWE-120)
- CVSS
- 9.8
- nvd
- EPSS
- —
- KEV
- No
- Class
- other
- CWE-120, CWE-120
Description
Memory safety bugs present in 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 was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Search profile — drives PoC discovery
Symbols bug_id=2004652bug_id=2019372bug_id=2021922bug_id=2022567bug_id=2022733mfsa2026-20mfsa2026-22mfsa2026-23mfsa2026-24
Keywords CVE-2026-4720Firefox 148 memory corruptionFirefox ESR 140.8 memory safetyThunderbird 148 memory corruptionThunderbird ESR 140.8 buffer overflowMozilla memory safety bugs 2026Firefox 149 fix memory corruptionFirefox ESR 140.9 patchmfsa2026-20 PoCmfsa2026-22 PoCmfsa2026-23 PoCmfsa2026-24 PoCCWE-120 Firefox 2026
Versions: Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, Thunderbird ESR < 140.9
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2004652%2C2019372%2C2021922%2C2022567%2C2022733
- https://www.mozilla.org/security/advisories/mfsa2026-20/
- https://www.mozilla.org/security/advisories/mfsa2026-22/
- https://www.mozilla.org/security/advisories/mfsa2026-23/
- https://www.mozilla.org/security/advisories/mfsa2026-24/
- https://access.redhat.com/errata/RHSA-2026:5930
- https://access.redhat.com/errata/RHSA-2026:5931
- https://access.redhat.com/errata/RHSA-2026:5932
- https://access.redhat.com/errata/RHSA-2026:6188
- https://access.redhat.com/errata/RHSA-2026:6342
- https://access.redhat.com/errata/RHSA-2026:6917
- https://access.redhat.com/errata/RHSA-2026:7837
Status: enriched · ingested 2026-06-30T06:00:22.000Z · profiled 2026-07-01T18:30:14.000Z