CVE-2026-63816 (GCVE-0-2026-63816)

Vulnerability from cvelistv5 – Published: 2026-07-19 12:02 – Updated: 2026-08-17 04:51
VLAI
Title
f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode
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.
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: 3db1de0e582c358dd013f3703cd55b5fe4076436 , < 7d3ae21783e5914c1761ac7d63f882d3d70800e9 (git)
Affected: 3db1de0e582c358dd013f3703cd55b5fe4076436 , < 56038756aae68312df00d4aa1d97e51ef3aca725 (git)
Affected: 3db1de0e582c358dd013f3703cd55b5fe4076436 , < a499f77c06050a28c897bdbd86cd2f0721ae0743 (git)
Affected: 3db1de0e582c358dd013f3703cd55b5fe4076436 , < a805fec35c201c59643ddcde713bce4051c8ee27 (git)
Affected: 3db1de0e582c358dd013f3703cd55b5fe4076436 , < e0288584baa5dc41df4a829a023c4c1b33fe53d7 (git)
Affected: 6db52f1944417c2601182a591a704e2f119c5215 (git)
Affected: 5.18.18 , < 5.19 (semver)
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Linux Linux Affected: 5.19
Unaffected: 0 , < 5.19 (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.96 , ≤ 6.12.* (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 7.1.3 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
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              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "versionStartIncluding": "5.19",
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                },
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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",
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    "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",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-63816",
      "date": "2026-09-22",
      "epss": "0.00126",
      "percentile": "0.02676"
    },
    "microsoft_vex": {
      "current_release_date": "2026-08-13T00:15:21.000Z",
      "cve": "CVE-2026-63816",
      "id": "msrc_CVE-2026-63816",
      "initial_release_date": "2026-07-20T01:01:36.000Z",
      "product_status:known_not_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63816.json",
      "version": "3"
    },
    "nvd": {
      "cve": {
        "affected": [
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            "affectedData": [
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                "defaultStatus": "unaffected",
                "product": "Linux",
                "programFiles": [
                  "fs/f2fs/gc.c",
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                  },
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                    "versionType": "git"
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                  },
                  {
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                    "version": "6db52f1944417c2601182a591a704e2f119c5215",
                    "versionType": "git"
                  },
                  {
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                    "status": "affected",
                    "version": "5.18.18",
                    "versionType": "semver"
                  }
                ]
              },
              {
                "defaultStatus": "affected",
                "product": "Linux",
                "programFiles": [
                  "fs/f2fs/gc.c",
                  "fs/f2fs/inode.c"
                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                "vendor": "Linux",
                "versions": [
                  {
                    "status": "affected",
                    "version": "5.19"
                  },
                  {
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                    "status": "unaffected",
                    "version": "0",
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                  {
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                    "versionType": "semver"
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                    "versionType": "semver"
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                  }
                ]
              }
            ],
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
          }
        ],
        "cveTags": [],
        "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."
          }
        ],
        "id": "CVE-2026-63816",
        "lastModified": "2026-08-17T05:17:18.870",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-07-19T12:16:54.643",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/56038756aae68312df00d4aa1d97e51ef3aca725"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/7d3ae21783e5914c1761ac7d63f882d3d70800e9"
          },
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e0288584baa5dc41df4a829a023c4c1b33fe53d7"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-07-24T16:08:36+00:00",
      "cve": "CVE-2026-63816",
      "id": "CVE-2026-63816",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63816.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-21T13:04:52Z",
      "cve": "CVE-2026-63816",
      "id": "CVE-2026-63816",
      "initial_release_date": "2026-07-19T17:34:49Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63816",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63816.json",
      "version": "3"
    }
  }
}



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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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