CVE-2026-43303: mm/page_alloc: clear page->private in free_pages_prepare()

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: 2026-05-08 · updated 2026-10-19
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: mm/page_alloc: clear page->private in free_pages_prepare() Several subsystems (slub, shmem, ttm, etc.) use page->private but don't clear it before freeing pages. When these pages are later allocated as high-order pages and split via split_page(), tail pages retain stale page->private values. This causes a use-after-free in the swap subsystem. The swap code uses page->private to track swap count continuations, assuming freshly allocated pages have page->private == 0. When stale values are present, swap_count_continued() incorrectly assumes the continuation list is valid and iterates over uninitialized page->lru containing LIST_POISON values, causing a crash: KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107] RIP: 0010:__do_sys_swapoff+0x1151/0x1860 Fix this by clearing page->private in free_pages_prepare(), ensuring all freed pages have clean state regardless of previous use.

Affected products

Linux kernel: from 5.18.1 before 6.18.16; from 6.19 before 6.19.6; 5.18, 5.18-rc4, 5.18-rc5, 5.18-rc6, 5.18-rc7, 5.18-rc9 — fixed in 6.18.16, 6.19.6

How to fix

Upgrade to a fixed version: Linux kernel 6.18.16, 6.19.6. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-43303 or the next vulnerability affects your stack