CVE-2025-1942
Mozilla Firefox ≤ 136.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2025-1942 is a critical-severity Use of Uninitialized Resource (CWE-908) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique OS Credential Dumping (T1003); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-1942 is a critical vulnerability (CVSS 9.8) in the String.toUpperCase() implementation within Mozilla's JavaScript engine, where converting a string to uppercase that results in a longer output could incorporate uninitialized memory into the resulting string (CWE-908). This affects Firefox and Thunderbird versions prior to 136.
Remote attackers can exploit this vulnerability over the network with low complexity, requiring no privileges or user interaction (AV:N/AC:L/PR:N/UI:N/S:U). Successful exploitation enables high-impact confidentiality, integrity, and availability violations (C:H/I:H/A:H), potentially allowing arbitrary memory read via crafted JavaScript input that triggers the faulty string expansion.
Mozilla addressed the issue in Firefox 136 and Thunderbird 136, as detailed in security advisories MFSA 2025-14 and MFSA 2025-17, along with the upstream bug report at Bugzilla #1947139. Security practitioners should prioritize updating affected browsers to mitigate remote code execution or information disclosure risks.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-7444
Vulnerability Data
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (including static analysis) can find uses of uninitialized resources after they are coded.
Requiring documented development standards and tools can mandate initialization checks and safe patterns that stop the weakness from being introduced.
Engineering principles can require explicit resource initialization before use, structurally avoiding uninitialized access.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC activities such as static analysis and code review directly prevent use of uninitialized resources while also addressing many other weaknesses.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance can detect uninitialized resource usage through dynamic analysis and fuzzing.
Secure development life cycle mandates initialization checks and static analysis that can catch uninitialized resource use.
Application security requirements can specify mandatory initialization of variables and resources before use.
Secure system architecture and engineering principles include defensive coding practices that prevent use of uninitialized memory or objects.
Secure coding standards directly require explicit initialization of all variables and resources, substantially mitigating CWE-908.