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 affects Firefox < 138, Firefox ESR < 128.10, Thunderbird < 138, and Thunderbird ESR < 128.10.

Classification

CVE ID: CVE-2025-4091

CVSS Base Severity: MEDIUM

CVSS Base Score: 6.5

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected Products

Vendor: Mozilla

Product: Firefox, Firefox ESR, Thunderbird, Thunderbird ESR

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.08% (probability of being exploited)

EPSS Percentile: 23.46% (scored less or equal to compared to others)

EPSS Date: 2025-05-28 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-4091
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1951161%2C1952105
https://www.mozilla.org/security/advisories/mfsa2025-28/
https://www.mozilla.org/security/advisories/mfsa2025-29/
https://www.mozilla.org/security/advisories/mfsa2025-31/
https://www.mozilla.org/security/advisories/mfsa2025-32/

Timeline