Vulnerability Description
Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9. 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 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird 128.10.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | < 128.10 |
| Mozilla | Thunderbird | < 128.10.0 |
Related Weaknesses (CWE)
References
- https://bugzilla.mozilla.org/buglist.cgi?bug_id=1951161%2C1952105Broken Link
- https://www.mozilla.org/security/advisories/mfsa2025-28/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-29/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-31/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2025-32/Vendor Advisory
- https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html
FAQ
What is CVE-2025-4091?
CVE-2025-4091 is a vulnerability with a CVSS score of 8.1 (HIGH). Memory safety bugs present in Firefox 137, Thunderbird 137, Firefox ESR 128.9, and Thunderbird 128.9. Some of these bugs showed evidence of memory corruption and we presume that with enough effort som...
How severe is CVE-2025-4091?
CVE-2025-4091 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-4091?
Check the references section above for vendor advisories and patch information. Affected products include: Mozilla Firefox, Mozilla Thunderbird.