CVE-2023-20593 (Cross-Process Information Leak on AMD Zenbleed systems) was published in the official security bulletin on July 25th, 2023. Please read this security blog to learn more about this vulnerability.
Table of content:
2. Mitigation guide for CloudLinux OS
3. Updates as of August 3, 2023 - clarification on OS versions required for mitigation
4. Updates as of August 11, 2023 - update command for CloudLinux OS 7 hybrid added
The Zenbleed vulnerability, known as CVE-2023-20593 , allows data to be stolen at a rate of 30kb per second for each CPU core. This means it can quickly and effectively steal sensitive information that the CPU is handling. The risk is widespread and affects all software that operates on the compromised processor, such as virtual machines, sandboxes, containers, and processes. The fact that this attack can steal data from many virtual machines at once is causing a lot of concern for both cloud service providers and their users.
Every Zen 2 CPU, inclusive of EPYC Rome processors, is at risk to this vulnerability, as per Ormandy's statements:
The vulnerability can be exploited via arbitrary code execution that doesn't require elevated permissions. Ormandy has made available a repository of security research and exploit code. The exploit works by altering the register files to cause a mispredicted command.
You can mitigate the issue by executing the following instructions:
For CloudLinux 8 and 9 updated microcode is already in stable, to update run:
dnf update linux-firmware
echo 1 > /sys/devices/system/cpu/microcode/reload
For CloudLinux 7 updated microcode is in beta (ETA for Stable repo is August 7, 2023),
to update run:
yum install --enablerepo=cloudlinux-updates-testing linux-firmware
echo 1 > /sys/devices/system/cpu/microcode/reload
To check that the installation was completed successfully, you can run:
rpm -qa linux-firmware
Note!
Patches fix Zenbleed vulnerability only on AMD EPYC “Rome” Processors.
Patches for others mentioned processors will be available in the next releases of microcode.
We will keep you posted on the latest updates.
For CloudLinux OS 7h update run the following commands:
yum install --enablerepo=cl7h_beta linux-firmwareecho 1 > /sys/devices/system/cpu/microcode/reload
Update as of Aug 3, 2023: