CVE-2026-43303 mm/page_alloc: clear page->private in free_pages_prepare()
A use-after-free vulnerability in the Linux kernel swap subsystem allows local attackers to cause a system crash by exploiting stale page private data.
- 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
What is CVE-2026-43303?
CVE-2026-43303 is a high-severity use after free vulnerability in Linux kernel, published on 8 May 2026. 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:
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.
Which versions are affected by CVE-2026-43303?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43303?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-43303 being exploited?
There is no known exploitation of CVE-2026-43303 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-86160, BELL-CVE-2026-43303, DEBIAN-CVE-2026-43303, GHSA-6fh9-96ww-pvwq, ROOT-OS-DEBIAN-12-CVE-2026-43303, ROOT-OS-DEBIAN-13-CVE-2026-43303 and 2 more.