CVE-2023-53438: In the Linux kernel, the following vulnerability has been resolved: x86/MCE: Always save CS register on AMD Zen IF Poison errors The Instruction Fet...

Description

In the Linux kernel, the following vulnerability has been resolved: x86/MCE: Always save CS register on AMD Zen IF Poison errors The Instruction Fetch (IF) units on current AMD Zen-based systems do not guarantee a synchronous #MC is delivered for poison consumption errors. Therefore, MCG_STATUS[EIPV|RIPV] will not be set. However, the microarchitecture does guarantee that the exception is delivered within the same context. In other words, the exact rIP is not known, but the context is known to not have changed. There is no architecturally-defined method to determine this behavior. The Code Segment (CS) register is always valid on such IF unit poison errors regardless of the value of MCG_STATUS[EIPV|RIPV]. Add a quirk to save the CS register for poison consumption from the IF unit banks. This is needed to properly determine the context of the error. Otherwise, the severity grading function will assume the context is IN_KERNEL due to the m->cs value being 0 (the initialized value). This leads to unnecessary kernel panics on data poison errors due to the kernel believing the poison consumption occurred in kernel context.

Metrics

CVSS 3.1

5.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.14%

3.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	< 6.1.53
Linux	Linux Kernel	>= 6.2, < 6.4.16
Linux	Linux Kernel	>= 6.5, < 6.5.3

References

Timeline

Published: Sep 18, 2025
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-53438?

In the Linux kernel, the following vulnerability has been resolved: x86/MCE: Always save CS register on AMD Zen IF Poison errors The Instruction Fetch (IF) units on current AMD Zen-based systems do not guarantee a synchronous #MC is delivered for poison consumption errors. Therefore, MCG_STATUS[EIPV|RIPV] will not be set. However, the microarchitecture does guarantee that the exception is delivered within the same context. In other words, the exact rIP is not known, but the context is known to not have changed. There is no architecturally-defined method to determine this behavior. The Code Segment (CS) register is always valid on such IF unit poison errors regardless of the value of MCG_STATUS[EIPV|RIPV]. Add a quirk to save the CS register for poison consumption from the IF unit banks. This is needed to properly determine the context of the error. Otherwise, the severity grading function will assume the context is IN_KERNEL due to the m->cs value being 0 (the initialized value). This leads to unnecessary kernel panics on data poison errors due to the kernel believing the poison consumption occurred in kernel context.

How severe is CVE-2023-53438?

CVE-2023-53438 has a CVSS score of 5.5/10 (MEDIUM severity). The EPSS model estimates a 0.14% probability of exploitation in the next 30 days.

How do I fix CVE-2023-53438?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.