CVE-2025-1942

Disclosure of uninitialized memory when .toUpperCase() causes string to get longer

State: Published
Severity: 9.8 Critical
Published: Mar 4, 2025
Updated: Jun 4, 2026
Reserved: Mar 4, 2025

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.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	CISA-ADP

Weaknesses

CWE-908 Use of Uninitialized Resource

Affected Products

Product	Versions
FirefoxMozilla	136 and laterNot affected
ThunderbirdMozilla	136 and laterNot affected

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1947139
https://www.mozilla.org/security/advisories/mfsa2025-14/
https://www.mozilla.org/security/advisories/mfsa2025-17/

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