CVE-2026-43303 (GCVE-0-2026-43303)

Vulnerability from cvelistv5 – Published: 2026-05-08 13:11 – Updated: 2026-08-05 12:27
VLAI
Title
mm/page_alloc: clear page->private in free_pages_prepare()
Summary
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.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < e7790ab165713b79b1617ce659742ceb3a859d05 (git)
Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < 3edb8ebbf79b9016040e8f3421d723ae3d542b32 (git)
Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < f9719e32a67b4b00b3c9b133e8b5ffa72a26b67b (git)
Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < 23b82b7a26182ad840ae67d390d7ec9771e8c00f (git)
Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < d757c793853ec5483eb41ec2942c300b8fa720fb (git)
Affected: 3b8000ae185cb068adbda5f966a3835053c85fd4 , < ac1ea219590c09572ed5992dc233bbf7bb70fef9 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.16 , ≤ 6.18.* (semver)
Unaffected: 6.19.6 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/page_alloc: clear page-\u003eprivate in free_pages_prepare()\n\nSeveral subsystems (slub, shmem, ttm, etc.) use page-\u003eprivate but don\u0027t\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-\u003eprivate values.\n\nThis causes a use-after-free in the swap subsystem.  The swap code uses\npage-\u003eprivate to track swap count continuations, assuming freshly\nallocated pages have page-\u003eprivate == 0.  When stale values are present,\nswap_count_continued() incorrectly assumes the continuation list is valid\nand iterates over uninitialized page-\u003elru 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-\u003eprivate in free_pages_prepare(), ensuring all\nfreed pages have clean state regardless of previous use."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:L - The vulnerable swap continuation and page allocator paths are reached through local memory-management activity such as fork/swap/reclaim or swap administration, not by remote packets or physical access.\nAC:L - There is no attacker-uncontrolled race; a local attacker can repeatedly create swap pressure and duplicate swapped entries to drive the continuation path, and allocator grooming is under attacker influence.\nPR:L - Although swapon/swapoff require CAP_SYS_ADMIN in init_user_ns, the same vulnerable swap_count_continued() path is reachable by an unprivileged local user through normal swapped PTE duplication paths once swap is active.\nUI:N - No victim action is required after the attacker has local execution; the trigger can be driven by the attacker\u0027s own processes and memory activity.\nS:U - The impact remains within the kernel and the same host security authority; this is not a VM escape or cross-boundary IOMMU/DMA issue.\nC:H - The stale page-\u003eprivate value causes a use-after-free style interpretation of stale struct page list metadata, leading to wild kernel memory accesses that can plausibly be shaped into information disclosure.\nI:H - swap_count_continued() can write through a page derived from stale list pointers, making this kernel memory corruption with plausible arbitrary write/control-flow impact.\nA:H - The reported failure is a KASAN wild-memory-access crash in __do_sys_swapoff, and the same invalid list traversal can oops or panic the kernel."
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    "datePublished": "2026-05-08T13:11:23.561Z",
    "dateReserved": "2026-05-01T14:12:56.000Z",
    "dateUpdated": "2026-08-05T12:27:08.856Z",
    "state": "PUBLISHED"
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "mm/page_alloc: clear page-\u003eprivate in free_pages_prepare()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-43303.json",
      "version": "7"
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When stale values are present,\\nswap_count_continued() incorrectly assumes the continuation list is valid\\nand iterates over uninitialized page-\u003elru 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-\u003eprivate in free_pages_prepare(), ensuring all\\nfreed pages have clean state regardless of previous 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-09T13:55:08+00:00",
      "cve": "CVE-2026-43303",
      "id": "CVE-2026-43303",
      "initial_release_date": "2026-05-08T00:00:00+00:00",
      "product_status:fixed": "1658",
      "product_status:known_affected": "36",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm/page_alloc: clear page-\u003eprivate in free_pages_prepare()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-43303.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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