CVE-2026-42171: CWE-427 Uncontrolled Search Path Element in Nullsoft Nullsoft Scriptable Install System
CVE-2026-42171 is a high-severity vulnerability in Nullsoft Scriptable Install System (NSIS) versions before 3. 12, specifically 3. 06. 1. The issue arises because NSIS sometimes uses the Low Integrity Level (IL) temporary directory when running as SYSTEM. This behavior can allow a local attacker to gain elevated privileges if they can manipulate the function my_GetTempFileName to return 0. The vulnerability is categorized as CWE-427, indicating an uncontrolled search path element. No official patch or remediation guidance is currently available from the vendor.
AI Analysis
Technical Summary
The vulnerability CVE-2026-42171 affects NSIS 3.06.1 and earlier versions before 3.12. It involves the installer occasionally using the Low IL temp directory when executing with SYSTEM privileges. This can be exploited by a local attacker who can cause the my_GetTempFileName function to return 0, potentially leading to privilege escalation. The root cause is an uncontrolled search path element (CWE-427), which can allow execution of malicious code with elevated privileges. The CVSS v3.1 score is 7.8, reflecting high impact on confidentiality, integrity, and availability. No vendor advisory or patch links are currently provided.
Potential Impact
Successful exploitation of this vulnerability allows a local attacker to escalate privileges to SYSTEM level on affected NSIS versions. This can lead to full system compromise, including unauthorized access to sensitive data, modification of system files, and disruption of system availability. The CVSS score of 7.8 indicates a high impact on confidentiality, integrity, and availability. There are no known exploits in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official patch or remediation level is provided, users should monitor Nullsoft's official channels for updates. Until a fix is available, restrict local access to trusted users only and consider running installers with the least privileges necessary to reduce risk.
CVE-2026-42171: CWE-427 Uncontrolled Search Path Element in Nullsoft Nullsoft Scriptable Install System
Description
CVE-2026-42171 is a high-severity vulnerability in Nullsoft Scriptable Install System (NSIS) versions before 3. 12, specifically 3. 06. 1. The issue arises because NSIS sometimes uses the Low Integrity Level (IL) temporary directory when running as SYSTEM. This behavior can allow a local attacker to gain elevated privileges if they can manipulate the function my_GetTempFileName to return 0. The vulnerability is categorized as CWE-427, indicating an uncontrolled search path element. No official patch or remediation guidance is currently available from the vendor.
CVSS v3.1
Score 7.8high
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2026-42171 affects NSIS 3.06.1 and earlier versions before 3.12. It involves the installer occasionally using the Low IL temp directory when executing with SYSTEM privileges. This can be exploited by a local attacker who can cause the my_GetTempFileName function to return 0, potentially leading to privilege escalation. The root cause is an uncontrolled search path element (CWE-427), which can allow execution of malicious code with elevated privileges. The CVSS v3.1 score is 7.8, reflecting high impact on confidentiality, integrity, and availability. No vendor advisory or patch links are currently provided.
Potential Impact
Successful exploitation of this vulnerability allows a local attacker to escalate privileges to SYSTEM level on affected NSIS versions. This can lead to full system compromise, including unauthorized access to sensitive data, modification of system files, and disruption of system availability. The CVSS score of 7.8 indicates a high impact on confidentiality, integrity, and availability. There are no known exploits in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official patch or remediation level is provided, users should monitor Nullsoft's official channels for updates. Until a fix is available, restrict local access to trusted users only and consider running installers with the least privileges necessary to reduce risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mitre
- Date Reserved
- 2026-04-24T21:20:35.145Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
- Epss Score
- 0.00005
- Epss Percentile
- 0.00209
- Epss Date
- 2026-04-26
- Gcve Source
- db.gcve.eu
Threat ID: 69ebe24487115cfb68759c48
Added to database: 4/24/2026, 9:36:04 PM
Last enriched: 5/2/2026, 7:34:31 AM
Last updated: 6/8/2026, 9:14:53 PM
Views: 110
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