Vulnerability · Published Apr 24, 2026 · Assigned by mitre
CVE-2026-42171
High 7.8
In plain English
A high-severity uncontrolled search path in Nullsoft Scriptable Install System from Nullsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)7.8High
Exploit odds (30 days)0.2%top 88.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
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).
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | nsis | no fix listed | DEBIAN-CVE-2026-42171 |
| Debian:13 | nsis | no fix listed | DEBIAN-CVE-2026-42171 |
| Debian:14 | nsis | 3.12-1 | DEBIAN-CVE-2026-42171 |
| Ubuntu:22.04:LTS | nsis | no fix listed | UBUNTU-CVE-2026-42171 |
| Ubuntu:24.04:LTS | nsis | no fix listed | UBUNTU-CVE-2026-42171 |
| Ubuntu:25.10 | nsis | no fix listed | UBUNTU-CVE-2026-42171 |
| Ubuntu:26.04:LTS | nsis | no fix listed | UBUNTU-CVE-2026-42171 |
| Ubuntu:26.10 | nsis | no fix listed | UBUNTU-CVE-2026-42171 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Nullsoft | Nullsoft Scriptable Install System | 3.06.1 – before 3.12 |
Weakness: CWE-427 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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