AMD Processors Exposed to Critical Bug: Zenbleed Vulnerability Unveiled
A serious bug in AMD processors has been discovered by Tavis Ormandy, an experienced bug-hunter from Google. Named Zenbleed, this speculative execution bug affects a range of AMD Ryzen and Epic Zen 2 chips. Ormandy’s technical write-up of the bug reveals that it can potentially expose user credentials, including usernames and passwords, while logins are being processed.
According to Ormandy, the bug can leak approximately 30kb of data per core, per second, making it fast enough to monitor encryption keys and passwords during user logins. The vulnerability allows an attacker logged into a cloud machine to exploit Zenbleed and spy on other tenants without needing special privileges. Ormandy also suggests that a malicious web page could serve as a possible attack vector.
The bug is linked to a specific CPU instruction known as VZEROUPPER, which is responsible for zeroing the upper 128 bits of the YMM registers. Ormandy explains that mispredictions in the instruction’s execution can lead to severe security consequences. The bug has been confirmed on several AMD processors, including Ryzen Threadripper PRO 3945WX 12-Cores; Ryzen 7 PRO 4750GE with Radeon Graphics; Ryzen 7 5700U; and EPYC 7B12.
Ormandy informed AMD about the bug back in May, and the company has released a microcode patch to address the issue. In addition to AMD’s patch, vendors like Citrix have also issued hotfixes to mitigate the CPU hardware issue. Although Citrix clarifies that the bug doesn’t directly impact its Hypervisor product, they still recommend applying the hotfix for systems running Citrix Hypervisor on AMD Zen 2 CPUs.
The discovery of Zenbleed highlights the importance of promptly addressing and patching vulnerabilities in processor architecture. While AMD has taken steps to fix the bug, it is crucial for users and organizations to install the necessary patches and updates to ensure their systems are protected. As more details emerge, it is advised to stay updated with the latest information regarding Zenbleed and any potential risks associated with it.
In conclusion, the Zenbleed vulnerability reveals a critical bug in AMD processors, potentially exposing user credentials during logins. The bug affects various AMD Ryzen and Epic Zen 2 chips, and while AMD has released a patch, users should remain vigilant and implement necessary updates to safeguard their systems.
