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CVE-2026-72172: mm/mm_init: fix uninitialized struct pages for ZONE_DEVICE

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-15 · updated 2026-10-16

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.

Affected products

• Linux kernel: 5.19 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.2. Check the vendor advisory for mitigations.

References

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

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