CVE-2024-13961: Local Privilege Escalation Vulnerability in Avast Cleanup Premium

Overview

The CVE-2024-13961 vulnerability is a critical security flaw found in Avast Cleanup Premium Version 24.2.16593.17810 on Windows 10 Pro x64. This vulnerability can be exploited by local attackers to escalate their privileges and execute arbitrary code in the context of SYSTEM. It has serious implications for the security of any system running the affected software as it could potentially lead to system compromise or data leakage, making it a high-risk vulnerability that needs to be addressed immediately.

Vulnerability Summary

CVE ID: CVE-2024-13961
Severity: High (CVSS: 7.8)
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Impact: System compromise and potential data leakage

Affected Products

Product | Affected Versions

Avast Cleanup Premium | 24.2.16593.17810

How the Exploit Works

This vulnerability is caused by a TOCTTOU (time-of-check to time-of-use) flaw in the TuneupSvc component of Avast Cleanup Premium. An attacker can exploit this flaw by creating a symbolic link and leveraging a race condition. This allows them to escalate their privileges and execute arbitrary code in the context of SYSTEM, effectively gaining full control over the affected system.

Conceptual Example Code

The exact mechanics of the exploit depend on the specific environment, but the general idea is shown in the pseudocode below:

// Attacker creates a symbolic link
create_symlink("/path/to/vulnerable/file", "/path/to/attacker/controlled/file");
// Attacker leverages TOCTTOU race condition
while(true) {
if (check_file_access("/path/to/vulnerable/file")) {
execute_code_as_system("/path/to/attacker/controlled/file");
break;
}
}

In this pseudocode, the `create_symlink` function creates a symbolic link from a file in a location that the TuneupSvc component is known to write to a file that the attacker controls. The `check_file_access` function checks if the TuneupSvc component is about to write to the file, and if it is, the `execute_code_as_system` function is called to execute arbitrary code in the context of SYSTEM.

Mitigation and Prevention

The vendor has released a patch to address this vulnerability, and all users are strongly urged to apply this patch immediately. As a temporary measure before the patch can be applied, users can make use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to help mitigate potential attacks. However, these are only temporary solutions and the patch should be applied as soon as possible to fully mitigate the vulnerability.