Security Experts:

Microsoft Patches for CPU Flaws Break Windows, Apps

Users have complained that the updates released by Microsoft last week for the Spectre and Meltdown vulnerabilities cause Windows to break down on some computers with AMD processors.

Several individuals whose computers rely on AMD processors, particularly older Athlon models, say they are unable to start Windows 10 after installing KB4056892, an update released by Microsoft in response to the disclosure of serious flaws affecting Intel, AMD and ARM processors.

The security holes have been dubbed Spectre and Meltdown and they allow malicious applications to bypass memory isolation mechanisms and access passwords, photos, documents, emails, and other sensitive information. Both local and remote exploitation are possible.

Users have reported that after installing Microsoft’s update the operating system freezes during boot when the Windows logo is displayed. Some users claimed to have had problems reverting to a previous state, and those who did manage to do it warned that the automatic update feature needs to quickly be disabled to prevent the update from being reinstalled.

While a majority of the affected users appear to have older AMD Athlon processors, some devices with AMD Turion CPUs also appear to have been hit.

Microsoft has not shared any information regarding this issue. A Microsoft spokesperson told SecurityWeek that the company is aware of the reports and is investigating.

Users have reported other problems as well after installing KB4056892. Owners of Asus devices say they receive an error message related to an Asus utility after updating.

The Spectre/Meltdown updates appear to break the PulseSecure VPN on both Windows 10 and Windows 8.1 – the patch for Windows 8.1 is included in KB4056898. The VPN vendor has released patches to address the issue.

Some Windows users report that they simply cannot install the patches for the CPU vulnerabilities, and some say their web browsers have started crashing after applying the update.

Shortly after releasing the Meltdown/Spectre updates, Microsoft warned that it had identified some compatibility issues with some antivirus products. The company informed users that if they had not been offered the security updates, they may be running an incompatible antivirus application.

*updated with statement from Microsoft

Related: Qualcomm Working on Mitigations for Spectre, Meltdown

Related: Lawsuits Filed Against Intel Over CPU Vulnerabilities

Related: Industry Reactions to Meltdown, Spectre Attacks

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Eduard Kovacs is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.