CVE-2026-63816 (GCVE-0-2026-63816)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-08-17 04:51
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode - ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink - f2fs_gc - gc_data_segment - ra_data_block(cow_inode) - mapping = F2FS_I(inode)->atomic_inode->i_mapping : f2fs_is_cow_file(cow_inode) is true - f2fs_evict_inode(atomic_inode) - clear_inode_flag(fi->cow_inode, FI_COW_FILE) - F2FS_I(fi->cow_inode)->atomic_inode = NULL ... - truncate_inode_pages_final(atomic_inode) - f2fs_grab_cache_folio(mapping) : create folio in atomic_inode->mapping - clear_inode(atomic_inode) - BUG_ON(atomic_inode->i_data.nrpages) We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue.
References
Impacted products
Vendor Product Version
Linux Linux Version: 3db1de0e582c358dd013f3703cd55b5fe4076436
Version: 3db1de0e582c358dd013f3703cd55b5fe4076436
Version: 3db1de0e582c358dd013f3703cd55b5fe4076436
Version: 3db1de0e582c358dd013f3703cd55b5fe4076436
Version: 3db1de0e582c358dd013f3703cd55b5fe4076436
Version: 6db52f1944417c2601182a591a704e2f119c5215
Version: 5.18.18   ≤
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/gc.c",
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          ],
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          "vendor": "Linux",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "7.1.3",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.145",
                  "versionStartIncluding": "5.19",
                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode\n\n- ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE)\t\t- shrink\n - f2fs_gc\n  - gc_data_segment\n   - ra_data_block(cow_inode)\n    - mapping = F2FS_I(inode)-\u003eatomic_inode-\u003ei_mapping\n    : f2fs_is_cow_file(cow_inode) is true\n\t\t\t\t\t\t - f2fs_evict_inode(atomic_inode)\n\t\t\t\t\t\t  - clear_inode_flag(fi-\u003ecow_inode, FI_COW_FILE)\n\t\t\t\t\t\t  - F2FS_I(fi-\u003ecow_inode)-\u003eatomic_inode = NULL\n\t\t\t\t\t\t  ...\n\t\t\t\t\t\t  - truncate_inode_pages_final(atomic_inode)\n    - f2fs_grab_cache_folio(mapping)\n    : create folio in atomic_inode-\u003emapping\n\t\t\t\t\t\t  - clear_inode(atomic_inode)\n\t\t\t\t\t\t   - BUG_ON(atomic_inode-\u003ei_data.nrpages)\n\nWe need to add a reference on fi-\u003eatomic_inode before using its mapping\nfield during garbage collection, otherwise, it will cause UAF issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires local access through filesystem syscalls and ioctls (atomic-write ioctls, file I/O, close/evict) on an F2FS mount; there is no network-facing entry point to the vulnerable GC path.\nAC:L - The attacker controls both sides of the race by running concurrent threads that perform atomic writes/commits/closes while filling the filesystem or driving writes to trigger background or foreground GC via f2fs_balance_fs and the f2fs_gc kthread.\nPR:L - No real root is required; an unprivileged local user with write access to their own files on F2FS can use atomic-write ioctls and normal I/O to reach the bug, while GC runs automatically without CAP_SYS_ADMIN.\nUI:N - The attacker can trigger the full exploit chain on files they own without any separate victim user performing actions; atomic-write setup, GC pressure, and inode eviction are all orchestrated by the attacker process.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel security boundary, not a cross-VM or cross-container escape to a different security authority.\nC:H - This is a use-after-free on a live inode address_space; the freed atomic_inode can be reused or read through stale mapping pointers, enabling arbitrary kernel memory disclosure primitives.\nI:H - UAF on inode mapping during folio allocation allows heap corruption and control of freed object contents, which is exploitable for arbitrary kernel write and local privilege escalation.\nA:H - The race reliably leads to kernel BUG_ON in clear_inode when nrpages is nonzero, and UAF corruption can cause kernel oops or panic even before full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:23.480Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7d3ae21783e5914c1761ac7d63f882d3d70800e9"
        },
        {
          "url": "https://git.kernel.org/stable/c/56038756aae68312df00d4aa1d97e51ef3aca725"
        },
        {
          "url": "https://git.kernel.org/stable/c/a499f77c06050a28c897bdbd86cd2f0721ae0743"
        },
        {
          "url": "https://git.kernel.org/stable/c/a805fec35c201c59643ddcde713bce4051c8ee27"
        },
        {
          "url": "https://git.kernel.org/stable/c/e0288584baa5dc41df4a829a023c4c1b33fe53d7"
        }
      ],
      "title": "f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63816",
    "datePublished": "2026-07-19T12:02:15.907Z",
    "dateReserved": "2026-07-19T07:54:57.014Z",
    "dateUpdated": "2026-08-17T04:51:23.480Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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