Security News > 2023 > July > AMD Zenbleed chip bug leaks secrets fast and easy

AMD has started issuing some patches for its processors affected by a serious silicon-level bug dubbed Zenbleed that can be exploited by rogue users and malware to steal passwords, cryptographic keys, and other secrets from software running on a vulnerable system.

Exploiting Zenbleed involves abusing speculative execution, though unlike the related Spectre family of design flaws, the bug is pretty easy to exploit.

Malware already running on a system, or a rogue logged-in user, can exploit Zenbleed without any special privileges and inspect data as it is being processed by applications and the operating system, which can include sensitive secrets, such as passwords.

As such these registers have all sorts of data flying through them, including passwords and keys.

If vzeroupper is speculatively executed - the processor anticipates it will need to run that instruction - it sets this zero bit and frees the registers in the register file for reuse.

With threads being scheduled all over the processor core complex, and with some clever exploit code, it is possible to cause vzeroupper to be incorrectly speculative executed, rewound, and data to leak by observing the content of those vector registers.

News URL

https://go.theregister.com/feed/www.theregister.com/2023/07/24/amd_zenbleed_bug/