Vulnerability in Mozilla Firefox
CVE-2025-1942
When String.toUpperCase() caused a string to get longer it was possible for uninitialized memory to be incorporated into the result string. This vulnerability was fixed in Firefox 136 and Thunderbird 136.
EPSS: 0.004 (35.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Mozilla Firefox — versions 136
- Mozilla Thunderbird — versions 136
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security@mozilla.org (Issue Tracking)
- security@mozilla.org (Vendor Advisory)
- security@mozilla.org (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-1942?
- CVE-2025-1942 is a critical-severity vulnerability in Mozilla Firefox, classified under Use of Uninitialized Resource. CVSS score: 9.8/10. Published 2025-03-04.
- How severe is CVE-2025-1942?
- Critical severity. CVSS v3 base score is 9.8 out of 10.
- Is CVE-2025-1942 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.