CVE-2026-64567

Estado: RecibidaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

btrfs: reject free space cache with more entries than pages

When loading a v1 free space cache, __load_free_space_cache() takes num_entries and num_bitmaps straight from the on-disk btrfs_free_space_header. That header is stored in the tree_root under a key with type 0, which the tree-checker has no case for, so neither count is validated before the load trusts it.

The load loops num_entries times and maps the next page whenever the current one runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which does io_ctl->pages[io_ctl->index++]. But pages[] is allocated in io_ctl_init() from the cache inode's i_size, not from num_entries:

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So if num_entries claims more records than the pages can hold, io_ctl->index runs off the end of pages[]. The write side never hits this because io_ctl_add_entry() and io_ctl_add_bitmap() both stop once io_ctl->index >= io_ctl->num_pages; the read side just never had the same check.

To trigger it, take a clean cache (num_entries = <N> here), set num_entries in the header to 0x10000, and fix up the leaf checksum so it still passes the tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and pages[] is a 16-pointer (kmalloc-128) array. The load now tries to read 65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the array:

free-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc() at line 565, which is why that is the frame KASAN names. The out-of-bounds slot is then treated as a struct page and handed to crc32c(), so the bad read turns into a GP fault.

Add the missing check to io_ctl_check_crc(), which is where both the entry loop and the bitmap loop end up. When num_entries is too large the load now fails like any corrupt cache: __load_free_space_cache() drops it and rebuilds the free space from the extent tree, so a valid cache is never rejected.

Detalles técnicos trazas, registros y código del informe original

	num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
	io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);

  BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)
  Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58
   io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)
   __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820)
   load_free_space_cache (fs/btrfs/free-space-cache.c:1017)
   caching_thread (fs/btrfs/block-group.c:880)
   btrfs_work_helper (fs/btrfs/async-thread.c:312)
   process_one_work
   worker_thread
   kthread
   ret_from_fork

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.12%
Percentil entre todas las CVEs puntuadas: 2
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1499.004 Application or System Exploitationimpact75 %
Impacto secundarioT1005 Data from Local Systemcollection65 %

Vulnerabilidad local (AV:L/PR:L) sin interacción permite escribir caché corrupto en disco para causar lectura fuera de límites, llevando a crash (DoS) o lectura de memoria del kernel durante el manejo de páginas.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Threat Intelligence Program Filter Network Traffic Execution Prevention Application Isolation and Sandboxing Exploit Protection Update Software

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-64567",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
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      "affectedData": [
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          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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          ],
          "defaultStatus": "unaffected"
        },
        {
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              "version": "5.15.216",
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            },
            {
              "status": "unaffected",
              "version": "6.1.183",
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              "lessThanOrEqual": "6.1.*"
            },
            {
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              "version": "6.6.148",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.101",
              "versionType": "semver",
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            },
            {
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              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.1.6",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/btrfs/free-space-cache.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-05T08:16:36.277",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/094734c7aaa2b36751dc32480a680a4952685e78",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/f9fef131fa3f59b857217f522fa5ea430d1b707c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: reject free space cache with more entries than pages\n\nWhen loading a v1 free space cache, __load_free_space_cache() takes\nnum_entries and num_bitmaps straight from the on-disk\nbtrfs_free_space_header. That header is stored in the tree_root under a key\nwith type 0, which the tree-checker has no case for, so neither count is\nvalidated before the load trusts it.\n\nThe load loops num_entries times and maps the next page whenever the current\none runs out, going through io_ctl_check_crc() -> io_ctl_map_page(), which\ndoes io_ctl->pages[io_ctl->index++]. But pages[] is allocated in\nio_ctl_init() from the cache inode's i_size, not from num_entries:\n\n\tnum_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);\n\tio_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);\n\nSo if num_entries claims more records than the pages can hold, io_ctl->index\nruns off the end of pages[]. The write side never hits this because\nio_ctl_add_entry() and io_ctl_add_bitmap() both stop once\nio_ctl->index >= io_ctl->num_pages; the read side just never had the same\ncheck.\n\nTo trigger it, take a clean cache (num_entries = <N> here), set num_entries\nin the header to 0x10000, and fix up the leaf checksum so it still passes\nthe tree-checker. The cache inode has i_size = 65536, so num_pages is 16 and\npages[] is a 16-pointer (kmalloc-128) array. The load now tries to read\n65536 entries, io_ctl->index walks up to 16, and pages[16] is read past the\narray:\n\n  BUG: KASAN: slab-out-of-bounds in io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n  Read of size 8 at addr ffff88800c833a80 by task kworker/u8:3/58\n   io_ctl_check_crc (fs/btrfs/free-space-cache.c:420 fs/btrfs/free-space-cache.c:565)\n   __load_free_space_cache (fs/btrfs/free-space-cache.c:655 fs/btrfs/free-space-cache.c:820)\n   load_free_space_cache (fs/btrfs/free-space-cache.c:1017)\n   caching_thread (fs/btrfs/block-group.c:880)\n   btrfs_work_helper (fs/btrfs/async-thread.c:312)\n   process_one_work\n   worker_thread\n   kthread\n   ret_from_fork\n\nfree-space-cache.c:420 is io_ctl_map_page(), inlined into io_ctl_check_crc()\nat line 565, which is why that is the frame KASAN names. The out-of-bounds\nslot is then treated as a struct page and handed to crc32c(), so the bad\nread turns into a GP fault.\n\nAdd the missing check to io_ctl_check_crc(), which is where both the entry\nloop and the bitmap loop end up. When num_entries is too large the load now\nfails like any corrupt cache: __load_free_space_cache() drops it and rebuilds\nthe free space from the extent tree, so a valid cache is never rejected."
    }
  ],
  "lastModified": "2026-08-19T17:20:16.587",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}