CVE-2026-4721: Vulnerability in Mozilla Firefox
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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
AI Analysis
Technical Summary
CVE-2026-4721 covers a set of memory safety bugs affecting Mozilla Firefox ESR 115.33, ESR 140.8, Thunderbird ESR 140.8, Firefox 148, and Thunderbird 148. These vulnerabilities include use-after-free and incorrect boundary conditions that may lead to memory corruption. The Mozilla Foundation fixed these issues in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The CVSS v3.1 score is 9.8 (critical), indicating high impact on confidentiality, integrity, and availability. The vendor advisory confirms the fixes and recommends updating to the patched versions.
Potential Impact
The vulnerabilities could lead to arbitrary code execution due to memory corruption, impacting confidentiality, integrity, and availability of affected systems. Exploitation could allow attackers to run code remotely without user interaction. No known exploits in the wild have been reported at this time.
Mitigation Recommendations
A fix is available. Users and administrators should update affected Mozilla Firefox and Thunderbird installations to Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, or Thunderbird 140.9 as appropriate. Applying these official updates fully mitigates the vulnerabilities.
CVE-2026-4721: Vulnerability in Mozilla Firefox
Description
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 was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
CVSS v3.1
Score 9.8critical
Affected software
pkg:github/mozilla/firefoxRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-4721 covers a set of memory safety bugs affecting Mozilla Firefox ESR 115.33, ESR 140.8, Thunderbird ESR 140.8, Firefox 148, and Thunderbird 148. These vulnerabilities include use-after-free and incorrect boundary conditions that may lead to memory corruption. The Mozilla Foundation fixed these issues in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9. The CVSS v3.1 score is 9.8 (critical), indicating high impact on confidentiality, integrity, and availability. The vendor advisory confirms the fixes and recommends updating to the patched versions.
Potential Impact
The vulnerabilities could lead to arbitrary code execution due to memory corruption, impacting confidentiality, integrity, and availability of affected systems. Exploitation could allow attackers to run code remotely without user interaction. No known exploits in the wild have been reported at this time.
Mitigation Recommendations
A fix is available. Users and administrators should update affected Mozilla Firefox and Thunderbird installations to Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, or Thunderbird 140.9 as appropriate. Applying these official updates fully mitigates the vulnerabilities.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-03-23T23:22:42.445Z
- Cvss Version
- null
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-20/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-21/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-22/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-23/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-24/","vendor":"Mozilla"},{"url":"https://access.redhat.com/security/cve/CVE-2026-4721","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8427","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7843","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8315","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:5931","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:6342","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:5932","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:6917","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7840","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8285","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7858","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8850","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7842","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8289","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7838","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8288","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7839","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8286","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7841","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8287","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7845","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8290","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:7837","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:8284","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:5930","vendor":"Red Hat"},{"url":"https://access.redhat.com/errata/RHSA-2026:6188","vendor":"Red Hat"}]
Threat ID: 69c28788f4197a8e3b320700
Added to database: 03/24/2026, 12:46:00 UTC
Last enriched: 07/15/2026, 09:29:08 UTC
Last updated: 07/31/2026, 19:22:59 UTC
Views: 100
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