We found a way to DLL sideload with cleanmgr.exe. Contribute to the development of this exploit by visiting the GitHub repository:
GitHub – Network-Sec/CVE-2025-21420-PoC
Practice Verified Code and Commands:
1. Exploit Setup:
- Clone the repository:
git clone https://github.com/Network-Sec/CVE-2025-21420-PoC.git cd CVE-2025-21420-PoC
- Compile the malicious DLL:
gcc -shared -o malicious.dll malicious.c
- Place the DLL in the same directory as
cleanmgr.exe.
2. Trigger the Exploit:
- Run
cleanmgr.exe:./cleanmgr.exe
- Observe the DLL sideloading behavior.
3. Mitigation Steps:
- Ensure `cleanmgr.exe` is running from a trusted directory.
- Use Windows Defender or other AV tools to scan for malicious DLLs:
MpCmdRun.exe -Scan -ScanType 3 -File C:\Path\To\cleanmgr.exe
4. Additional Commands:
- Check loaded DLLs in a process:
tasklist /m /fi "imagename eq cleanmgr.exe"
- Monitor process behavior with Process Monitor (ProcMon):
- Filter for `cleanmgr.exe` and look for DLL load events.
What Undercode Say:
The CVE-2025-21420 vulnerability highlights the risks associated with DLL sideloading in Windows systems, particularly through trusted utilities like cleanmgr.exe. This exploit demonstrates how attackers can leverage poorly secured directories or misconfigurations to load malicious DLLs, escalating privileges or executing arbitrary code. To mitigate such threats, always ensure that system utilities are running from secure locations and regularly audit DLL loading behavior.
For further hardening, consider implementing the following measures:
- Use AppLocker or Windows Defender Application Control (WDAC) to restrict DLL loading:
Set-AppLockerPolicy -XmlPolicy .\AppLockerPolicy.xml
- Enable Audit Mode to monitor DLL loads:
auditpol /set /subcategory:"Detailed Tracking" /success:enable
- Regularly update your system and apply patches to mitigate known vulnerabilities:
wuauclt /detectnow /updatenow
For advanced users, explore tools like Sysinternals Suite to analyze and secure your environment. Additionally, refer to Microsoft’s official documentation on DLL Security Best Practices for more insights.
Stay vigilant and proactive in securing your systems against such exploits. Always verify the integrity of your executables and maintain a robust security posture to defend against privilege escalation attacks.
References:
Hackers Feeds, Undercode AI
