Microsoft fixes Windows zero-day bug exploited in ransomware attacks: Report

Microsoft has fixed a zero-day vulnerability affecting all supported versions of Windows, which experts say hackers exploited to launch ransomware attacks, a new report said on Thursday.

In February, researchers discovered an attack using a zero-day vulnerability in the Microsoft Common Log File System (CLFS). A cybercriminal group used an exploit developed for different versions and builds of Windows OS, including Windows 11 and attempted to deploy a Nokoyawa ransomware attack, according to the cybersecurity firm Kaspersky.

Microsoft assigned `CVE-2023-28252` to the discovered zero-day bug.

Attackers used the CVE-2023-28252 vulnerability to elevate privileges and steal credentials from the Security Account Manager (SAM) database.

While most of the vulnerabilities are used by APTs (Advanced Persistent Threat), the researchers stated that this one turned out to be exploited for cybercrime purposes by a sophisticated group that carries out ransomware attacks.

"Cybercrime groups are becoming increasingly more sophisticated using zero-day exploits in their attacks. Previously it was primarily a tool of APTs, but now cybercriminals have the resources to acquire zero-days and routinely use them in attacks," said Boris Larin, Lead Security Researcher with the Global Research and Analysis Team (GReAT).

"It`s very important for businesses to download the latest patch from Microsoft as soon as possible, and use other methods of protection, such as EDR solutions," he added.

Moreover, the report said that the hackers also attempted to execute similar elevation of privilege exploits in attacks on different small and medium-sized businesses in the Middle East and North America, and previously in Asia regions.

The researchers said they saw at least five different exploits of this kind, which were used in attacks on retail and wholesale, energy, manufacturing, healthcare, software development and other industries.