CVE-2026-43303: mm/page_alloc: clear page->private in free_pages_prepare()
In the Linux kernel, the following vulnerability has been resolved:
mm/pagealloc: clear page->private in freepagesprepare()
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 splitpage(), 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, swapcountcontinued() incorrectly assumes the continuation list is valid and iterates over uninitialized page->lru containing LISTPOISON values, causing a crash:
KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107] RIP: 0010:dosysswapoff+0x1151/0x1860
Fix this by clearing page->private in freepagesprepare(), ensuring all freed pages have clean state regardless of previous use.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Modify mm/page_alloc::free_pages_prepare() to clear page->private before freeing pages (so freed pages have a clean state regardless of previous use).
Linux kernel (mm/page_alloc) clear page->private in free_pages_prepare() = enabled - Compensating control
If you cannot patch immediately, mitigate swap-related exposure by preventing swap usage (e.g., disable or avoid swap devices) to reduce the likelihood of the swap subsystem use-after-free manifesting.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-43303?
CVE-2026-43303 has been classified as a moderate severity vulnerability in the Linux kernel.
How do I fix CVE-2026-43303?
To fix CVE-2026-43303, update the Linux kernel to the latest version where the vulnerability has been patched.
What are the potential impacts of CVE-2026-43303?
The potential impacts of CVE-2026-43303 include unintentional information disclosure and memory corruption.
Which versions of the Linux kernel are affected by CVE-2026-43303?
CVE-2026-43303 affects multiple versions of the Linux kernel prior to the availability of the security patch.
How was CVE-2026-43303 discovered?
CVE-2026-43303 was discovered through code analysis of the page allocation subsystem in the Linux kernel.