CVE-2026-42171 Privilege escalation in Nullsoft Scriptable Install System
Local attackers can escalate privileges by exploiting insecure temp directory usage in NSIS when running as SYSTEM.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-42171?
CVE-2026-42171 is a high-severity vulnerability in Nullsoft Scriptable Install System, published on 24 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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).
Weakness: CWE-427
Which versions are affected by CVE-2026-42171?
It affects 1 product.
Products include Nullsoft Nullsoft Scriptable Install System.
How do I fix CVE-2026-42171?
Upgrade to a fixed version.
Is CVE-2026-42171 being exploited?
There is no known exploitation of CVE-2026-42171 in the wild and no public exploit code.
Other vulnerabilities in Nullsoft Scriptable Install System
Sources
Also known as DEBIAN-CVE-2026-42171, GHSA-594m-24qw-wfmp, UBUNTU-CVE-2026-42171.