CVE-2026-42171 PUBLISHED

Assigner: mitre
Reserved: 24.04.2026 Published: 24.04.2026 Updated: 25.04.2026

NSIS (Nullsoft Scriptable Install System) 3.06.1 before 3.12 sometimes uses the Low IL temp directory when executing as SYSTEM, allowing local attackers to gain privileges (if they can cause my_GetTempFileName to return 0, as shown in the references).

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS Score: 7.8

Attack Vector	Local	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	Nullsoft
Product	Nullsoft Scriptable Install System
Versions	Default: unaffected affected from 3.06.1 to 3.12 (excl.)

References

https://nsis.sourceforge.io/Docs/AppendixF.html#v3.12-cl
https://github.com/NSIS-Dev/nsis/commit/8e6f02205d5f22da6c7855dbfe59b2af667330ca
https://github.com/NSIS-Dev/nsis/blob/7359413009afd4f0fff472d841fc2f2cc0e0a5f8/Source/exehead/util.c#L475-L484
https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-gettempfilename

Problem Types

CWE-427 Uncontrolled Search Path Element CWE