Windows computers that support the VAES instruction set are affected. An update temporarily reduces the performance of AES-based operations significantly.
Microsoft warns Windows users of possible data loss. This affects systems with Windows 11 and Windows Server 2022 that are powered by current processors and support the VAES (Vector Advanced Encryption Standard) instruction set.
Vulnerable Windows devices use either AES-XTS (AES-XEX based tweaked codebook mode with ciphertext stealing) or AES-GCM (AES with Galois/Counter mode) for encryption. To prevent possible data corruption, users should install the preview and security updates released on 24 May and 14 June, respectively.
However, the updates in question have undesirable “side effects”, according to Microsoft. “After applying these updates, you may experience reduced performance for nearly a month after installation on Windows Server 2022 and Windows 11 (original version).”
The performance degradation is said to occur in features such as BitLocker, Transport Layer Security (especially load balancers), and disk data throughput in enterprise environments. According to Microsoft, AES-based operations can be slowed down by up to a factor of two. The preview update published on 23 June and the security update published on 12 July should provide a remedy.