A newly patched security flaw in Microsoft Windows, tracked as CVE-2024-38193, was exploited by the North Korean state-sponsored Lazarus Group. The vulnerability, found in the Windows Ancillary Function Driver (AFD.sys) for WinSock, allowed attackers to escalate privileges to gain SYSTEM access. Microsoft addressed the flaw in its Patch Tuesday update after being informed of the issue by Gen Digital researchers Luigino Camastra and Milánek. The flaw had a CVSS score of 7.8, marking it as a significant security risk.
The vulnerability was initially discovered in early June 2024, when researchers from Gen Digital identified unauthorized access to sensitive system areas. Lazarus Group leveraged the flaw to bypass security restrictions, using a rootkit called FudModule to evade detection. This rootkit allowed attackers to access areas typically unreachable by regular users and administrators. While the exact details of how the intrusions were carried out remain unclear, the attacks highlight the group’s evolving tactics.
This exploitation follows a similar pattern seen in February 2024, when Lazarus Group weaponized another privilege escalation flaw, CVE-2024-21338, in the Windows AppLocker driver (appid.sys). Both vulnerabilities allowed the attackers to execute arbitrary code and deploy FudModule, a rootkit integrated into Lazarus’ malware ecosystem. By taking advantage of flaws in existing drivers, rather than introducing vulnerable drivers, Lazarus Group avoided traditional security defenses.
The rootkit FudModule is reportedly delivered through a remote access trojan known as Kaolin RAT, which provides attackers with stealthy persistence in compromised systems. According to cybersecurity firm Avast, Lazarus Group has been careful in its use of FudModule, only deploying it selectively. The attacks represent an advanced threat, utilizing privilege escalation and evasion techniques to bypass Microsoft’s security measures, furthering the group’s goal of targeting sensitive systems.
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