vulnerability
MFSA2025-42 Firefox: Security Vulnerabilities fixed in Firefox 139 (CVE-2025-5268)
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 9 | (AV:N/AC:M/Au:N/C:C/I:C/A:C) | May 27, 2025 | May 28, 2025 | Apr 15, 2026 |
Severity
9
CVSS
(AV:N/AC:M/Au:N/C:C/I:C/A:C)
Published
May 27, 2025
Added
May 28, 2025
Modified
Apr 15, 2026
Description
Memory safety bugs present in Firefox 138, Thunderbird 138, Firefox ESR 128.10, and Thunderbird 128.10. 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 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.
Solution
mozilla-firefox-upgrade-139_0
Rapid7 Labs
2026 Global Threat Landscape Report
The predictive window has collapsed. Exploitation follows disclosure in days. See how attackers are accelerating and how to stay ahead.