Vulnerability Description
Memory safety bugs present in 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 was fixed in Firefox 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 140.9.1 |
| Mozilla | Thunderbird | < 140.9.1 |
Related Weaknesses (CWE)
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=2022369%2C2023026%2C2023545%2C20Broken LinkIssue Tracking
- https://www.mozilla.org/security/advisories/mfsa2026-25/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-27/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2026-28/
- https://www.mozilla.org/security/advisories/mfsa2026-29/
FAQ
What is CVE-2026-5734?
CVE-2026-5734 is a vulnerability with a CVSS score of 9.8 (CRITICAL). Memory safety bugs present in 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 en...
How severe is CVE-2026-5734?
CVE-2026-5734 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-5734?
Check the references section above for vendor advisories and patch information. Affected products include: Mozilla Firefox, Mozilla Thunderbird.