# CVE-2024-26603: x86/fpu: Stop relying on userspace for info to fault in xsave buffer

> A local attacker can cause a kernel infinite loop and system hang by manipulating user-space FPU state during signal return.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Feb 2024
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-26603, DEBIAN-CVE-2024-26603, GHSA-fq97-hv4f-crm6, UBUNTU-CVE-2024-26603

## What is CVE-2024-26603?

CVE-2024-26603 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Feb 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

x86/fpu: Stop relying on userspace for info to fault in xsave buffer

Before this change, the expected size of the user space buffer was
taken from fx_sw->xstate_size. fx_sw->xstate_size can be changed
from user-space, so it is possible construct a sigreturn frame where:

 * fx_sw->xstate_size is smaller than the size required by valid bits in
   fx_sw->xfeatures.
 * user-space unmaps parts of the sigrame fpu buffer so that not all of
   the buffer required by xrstor is accessible.

In this case, xrstor tries to restore and accesses the unmapped area
which results in a fault. But fault_in_readable succeeds because buf +
fx_sw->xstate_size is within the still mapped area, so it goes back and
tries xrstor again. It will spin in this loop forever.

Instead, fault in the maximum size which can be touched by XRSTOR (taken
from fpstate->user_size).

[ dhansen: tweak subject / changelog ]

Weakness: CWE-835 (Loop with Unreachable Exit Condition)

## Which versions are affected by CVE-2024-26603?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-26603?

Apply the vendor's patch.

## Is CVE-2024-26603 being exploited?

There is no known exploitation of CVE-2024-26603 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-26603 and fix it if it is affected.

What it is: CVE-2024-26603 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Feb 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-26603 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-26603/ (Markdown: https://insights.sbomify.com/CVE-2024-26603/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26603
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26603
- OSV: https://osv.dev/vulnerability/CVE-2024-26603

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-26603/
Summaries are generated and may contain mistakes; the official description above is the record.