Critical Vulnerability in Linux Kernel: Unchecked MSR Access in AMD MMCONFIG Range
Summary
CVE-2025-21913: In the Linux kernel, the following vulnerability has been resolved: x86/amd_nb: Use rdmsr_safe() in amd_get_mmconfig_range() Xen doesn't offer MSR_FAM10H_MMIO_CONF_BASE to all guests. Affects linux versions < 6.1.133-1. Fixed in 6.1.133-1. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The Linux kernel is the core component of Linux operating systems, managing hardware and system resources. It provides essential services for all other software running on the system. The kernel is crucial for system stability and performance. This vulnerability affects the kernel versions in Debian 12 and 13, specifically related to AMD's MMCONFIG range, which is used for memory-mapped configuration space access.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the handling of Model-Specific Registers (MSRs) for AMD processors. The issue arises from the use of the 'rdmsr_safe()' function in the 'amd_get_mmconfig_range()' method, which can lead to unchecked MSR access errors. This vulnerability is particularly problematic in virtualized environments like Xen, where not all guests are granted access to certain MSRs, leading to potential system instability and security risks. The warning generated indicates that an unchecked MSR access error occurred, which could expose the system to further vulnerabilities if exploited.
How To Fix
Minimum fixed version
6.1.133-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
Currently, there are no specific workarounds mentioned for this vulnerability. However, treating the MMCFG as disabled is considered the right course of action, as indicated in the vulnerability details.
Conclusion
The CVE-2025-21913 vulnerability in the Linux kernel poses significant risks related to unchecked MSR access in AMD processors. Users are encouraged to update their systems to the latest patched versions where available and to monitor for further updates in affected distributions.
See every vulnerability recorded for linux →
FAQ
The impact includes potential system instability and security risks due to unchecked MSR access in AMD processors.
The vulnerability affects Linux kernel versions in Debian 12 and 13.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
Yes, a patch is available for Debian 13 in version 6.12.19-1. Debian 12 does not have a patched version yet.
If immediate updates are not possible, monitor for updates and consider disabling MMCFG as a temporary measure.
Related vulnerabilities
Recent vulnerabilities recorded for linux.
