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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00467.

Exploitation none

Automatable yes

Technical Impact total

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Mozilla Firefox affected
Version Status Constraints
136 unaffected ≤ *
Mozilla Thunderbird affected
Version Status Constraints
136 unaffected ≤ *

Configuration 1 [-]

OR cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

No data.

No data.

Project Subscriptions

Vendors Products
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Firefox Subscribe
Thunderbird Subscribe
Advisories
Source ID Title
EUVD EUVD EUVD-2025-7444 When String.toUpperCase() caused a string to get longer it was possible for uninitialized memory to be incorporated into the result string This vulnerability affects Firefox < 136 and Thunderbird < 136.
Ubuntu USN Ubuntu USN USN-7334-1 Firefox vulnerabilities
Ubuntu USN Ubuntu USN USN-7991-1 Thunderbird vulnerabilities
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://bugzilla.mozilla.org/show_bug.cgi?id=1947139 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-1942 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-1942 cve-icon
https://www.mozilla.org/security/advisories/mfsa2025-14/ cve-icon cve-icon cve-icon
https://www.mozilla.org/security/advisories/mfsa2025-17/ cve-icon cve-icon
History

Mon, 13 Apr 2026 15:00:00 +0000

Type Values Removed Values Added
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 affects Firefox < 136 and Thunderbird < 136. 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.
Title firefox: Disclosure of uninitialized memory when .toUpperCase() causes string to get longer Disclosure of uninitialized memory when .toUpperCase() causes string to get longer

Fri, 28 Mar 2025 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
Vendors & Products Mozilla
Mozilla firefox
Mozilla thunderbird

Tue, 25 Mar 2025 14:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-908
Metrics cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

 cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Wed, 12 Mar 2025 17:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-908
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

 cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L'}

Wed, 05 Mar 2025 03:00:00 +0000

Type Values Removed Values Added
Title firefox: Disclosure of uninitialized memory when .toUpperCase() causes string to get longer
Weaknesses CWE-824
References
Metrics threat_severity

None

 threat_severity

Moderate

Wed, 05 Mar 2025 00:00:00 +0000

Type Values Removed Values Added
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 affects Firefox < 136. When String.toUpperCase() caused a string to get longer it was possible for uninitialized memory to be incorporated into the result string This vulnerability affects Firefox < 136 and Thunderbird < 136.
References

Tue, 04 Mar 2025 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-908
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 04 Mar 2025 13:45:00 +0000

Type Values Removed Values Added
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 affects Firefox < 136.
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: mozilla

Published:

Updated: 2026-04-13T14:30:28.192Z

Reserved: 2025-03-04T12:29:51.191Z

Link: CVE-2025-1942

cve-icon Vulnrichment

Updated: 2025-03-04T15:45:14.531Z

cve-icon NVD

Status : Modified

Published: 2025-03-04T14:15:39.167

Modified: 2026-04-13T15:16:53.940

Link: CVE-2025-1942

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-03-04T13:31:25Z

Links: CVE-2025-1942 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses