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Vulnerability record · CVE-2026-42171 · published 24 April 2026

CVE-2026-42171: Nullsoft scriptable install system uncontrolled search path element vulnerability

Nullsoft · Nullsoft Scriptable Install System

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).

7.8 CVSS 3.1 High EPSS 0.24% · top 86.6% CWE-427 · Uncontrolled search path element
7.8CVSS 3.1 base score
0.24%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

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).

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.8CVE-2015-9268Nullsoft scriptable install system improper input validation vulnerabilityNullsoft Scriptable Install System (NSIS) before 2.49 has unsafe implicit linking against Version.dll. In other words, there is no protection mechani…EPSS 1.5%5.5CVE-2015-9267Nullsoft scriptable install system improper privilege management vulnerabilityNullsoft Scriptable Install System (NSIS) before 2.49 uses temporary folder locations that allow unprivileged local users to overwrite files. This al…EPSS 0.39%5.3CVE-2023-37378Nullsoft scriptable install system vulnerabilityNullsoft Scriptable Install System (NSIS) before 3.09 mishandles access control for an uninstaller directory.EPSS 0.88%7.8CVE-2020-3433Cisco AnyConnect Windows client DLL hijacking via IPC channelCisco AnyConnect Secure Mobility Client for Windows fails to properly validate resources loaded at run time, allowing a DLL hijacking attack through …KEVEPSS 10%analysed6.5CVE-2020-3153Cisco AnyConnect Windows Installer Path Handling Privilege EscalationThe Cisco AnyConnect Secure Mobility Client for Windows installer mishandles directory paths, letting an authenticated local user copy attacker-suppl…KEVEPSS 28%analysed

Source: NIST National Vulnerability Database (record CVE-2026-42171), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.