Overview
CVE-2025-43715 is a significant security vulnerability that affects the Nullsoft Scriptable Install System (NSIS) on Windows platforms. This vulnerability allows local users to escalate their privileges to SYSTEM during an installation process. It pertains to how NSIS handles temporary plugins directory creation during installations, making it susceptible to race condition exploits. The vulnerability is of particular concern because it could potentially enable system compromise or data leakage, posing a serious risk to users and their sensitive information.
Vulnerability Summary
CVE ID: CVE-2025-43715
Severity: High (8.1 CVSS v3.0 Score)
Attack Vector: Local
Privileges Required: Low
User Interaction: Required
Impact: System compromise or data leakage
Affected Products
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Product | Affected Versions
Nullsoft Scriptable Install System | Before 3.11
How the Exploit Works
The exploit of CVE-2025-43715 revolves around the temporary plugins directory that NSIS creates under %WINDIR%\temp during an installation process. By winning a race condition, unprivileged users can place a crafted executable file in this directory. Since NSIS’s EW_CREATEDIR does not always set the CreateRestrictedDirectory error flag, this allows the system to execute the crafted file with elevated SYSTEM privileges, leading to a potential system compromise or data leakage.
Conceptual Example Code
Even though the actual exploit process involves wining a race condition and is complex to show in a simple code example, the conceptual pseudo-code below provides a simplified idea of how this vulnerability might be exploited:
# pseudo-code
import os
import shutil
# Locate the temporary plugins directory
temp_dir = os.environ['WINDIR'] + '/temp'
# Crafted executable content
crafted_exe = '...'
# Wait for the right moment (race condition)
while not os.path.exists(temp_dir):
pass
# Write the crafted executable to the temporary plugins directory
with open(os.path.join(temp_dir, 'crafted.exe'), 'w') as f:
f.write(crafted_exe)
# The crafted executable will be executed with SYSTEM privileges during NSIS installationMitigation Guidance
Users are recommended to apply the vendor-provided patch as soon as possible. If applying the patch immediately is not an option, using Web Application Firewalls (WAF) or Intrusion Detection Systems (IDS) can serve as a temporary mitigation measure. However, these do not completely remediate the vulnerability and are merely stopgap solutions. The only comprehensive solution is to update NSIS to a version that has addressed this vulnerability.