CVE-2026-42171: Nullsoft Scriptable Install System

High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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).

Affected products

• Nullsoft Nullsoft Scriptable Install System: from 3.06.1, before 3.12 (fixed in 3.12)

Published 2026-04-24. Last modified 2026-06-17.