CVE-2025-1942: Vulnerability in Mozilla Firefox
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.
AI Analysis
Technical Summary
The vulnerability CVE-2025-1942 involves the JavaScript String.toUpperCase() function in Mozilla Firefox. When this function caused the length of a string to increase, uninitialized memory could be included in the output string. This memory disclosure flaw could potentially expose sensitive information. Mozilla fixed this issue in Firefox 136 and Thunderbird 136. The CVSS 3.1 base score is 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating it is remotely exploitable without privileges or user interaction and can lead to high confidentiality, integrity, and availability impacts. The vendor advisories (MFSA 2025-14 and MFSA 2025-17) list this vulnerability among other memory safety bugs fixed in these versions.
Potential Impact
The vulnerability allows disclosure of uninitialized memory contents when the toUpperCase() method causes a string to grow. This could lead to leakage of sensitive information from memory. The CVSS score of 9.8 reflects critical impact on confidentiality, integrity, and availability. However, no known exploits in the wild have been reported. The flaw affects Firefox and Thunderbird prior to version 136.
Mitigation Recommendations
Mozilla has fixed this vulnerability in Firefox 136 and Thunderbird 136. Users and administrators should update to these versions or later to remediate the issue. Since the vendor advisory confirms the fix is available, applying the official update is the recommended mitigation. No additional workarounds or mitigations are indicated by the vendor.
CVE-2025-1942: Vulnerability in Mozilla Firefox
Description
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.
CVSS v3.1
Score 9.8critical
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2025-1942 involves the JavaScript String.toUpperCase() function in Mozilla Firefox. When this function caused the length of a string to increase, uninitialized memory could be included in the output string. This memory disclosure flaw could potentially expose sensitive information. Mozilla fixed this issue in Firefox 136 and Thunderbird 136. The CVSS 3.1 base score is 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating it is remotely exploitable without privileges or user interaction and can lead to high confidentiality, integrity, and availability impacts. The vendor advisories (MFSA 2025-14 and MFSA 2025-17) list this vulnerability among other memory safety bugs fixed in these versions.
Potential Impact
The vulnerability allows disclosure of uninitialized memory contents when the toUpperCase() method causes a string to grow. This could lead to leakage of sensitive information from memory. The CVSS score of 9.8 reflects critical impact on confidentiality, integrity, and availability. However, no known exploits in the wild have been reported. The flaw affects Firefox and Thunderbird prior to version 136.
Mitigation Recommendations
Mozilla has fixed this vulnerability in Firefox 136 and Thunderbird 136. Users and administrators should update to these versions or later to remediate the issue. Since the vendor advisory confirms the fix is available, applying the official update is the recommended mitigation. No additional workarounds or mitigations are indicated by the vendor.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2025-03-04T12:29:51.191Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2025-14/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2025-17/","vendor":"Mozilla"}]
Threat ID: 69dd057782d89c981f017282
Added to database: 04/13/2026, 15:02:15 UTC
Last enriched: 06/04/2026, 19:53:46 UTC
Last updated: 09/10/2026, 19:36:49 UTC
Views: 185
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