CVE-2026-89786 (GCVE-0-2026-89786)
Vulnerability from cvelistv5
Published
2026-09-16 08:48
Modified
2026-10-19 08:52
Severity ?
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: fix out-of-bounds read in ext4_read_inline_dir() ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64(): BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry Read of size 2 at addr ffff88800f3dd23c by task exploit/148 ... __ext4_check_dir_entry ext4_read_inline_dir iterate_dir The dirent payload lives in a buffer of exactly inline_size bytes: dir_buf = kmalloc(inline_size, GFP_NOFS); but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets. A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected. Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.
References
Impacted products
Vendor Product Version
Linux Linux Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
Version: c4d8b0235aa98f8c26bf94d308be3fdd24154572
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/inline.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "c4d8b0235aa98f8c26bf94d308be3fdd24154572",
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          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "version": "5.15.221",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.221",
                  "versionStartIncluding": "3.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.188",
                  "versionStartIncluding": "3.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
                  "versionStartIncluding": "3.10",
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                  "versionStartIncluding": "3.10",
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "3.10",
                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
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                  "versionEndExcluding": "7.3",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix out-of-bounds read in ext4_read_inline_dir()\n\next4_read_inline_dir() can read a dirent header past the end of its inline\nbuffer, triggering a slab-out-of-bounds read during getdents64():\n\n  BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry\n  Read of size 2 at addr ffff88800f3dd23c by task exploit/148\n   ...\n   __ext4_check_dir_entry\n   ext4_read_inline_dir\n   iterate_dir\n\nThe dirent payload lives in a buffer of exactly inline_size bytes:\n\n\tdir_buf = kmalloc(inline_size, GFP_NOFS);\n\nbut iteration runs in a position space extra_offset bytes larger\n(extra_size = extra_offset + inline_size) so the synthetic \".\" and \"..\"\nland at their block-dir offsets. A dirent is formed at \"dir_buf + pos -\nextra_offset\", yet the ext4_check_dir_entry() length argument uses the\nlarger extra_size. A position whose dirent header would extend past\nextra_size is therefore accepted, and the rescan loop\u0027s rec_len probe and\next4_check_dir_entry() dereference de-\u003erec_len before the entry is rejected.\n\nReject a position whose minimum-size dirent header would not fit within\nextra_size before forming de, in both the rescan and main loops, and pass\ninline_size rather than extra_size to ext4_check_dir_entry() so the length\ncheck matches the physical buffer."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The slab OOB is in ext4_read_inline_dir(), reached from getdents64 via iterate_dir\u2192ext4_readdir. nfsd_readdir does vfs_llseek plus iterate_dir, and ksmbd QUERY_DIRECTORY also calls iterate_dir, so a remote NFS/SMB client can trigger the same path on an ext4-backed export.\nAC:L - A crafted inline directory with attacker-controlled rec_len values (or a seek/NFS cookie that lands ctx-\u003epos near extra_size) deterministically forms a dirent past kmalloc(inline_size) and dereferences de-\u003erec_len. No race or attacker-uncontrollable heap layout is required.\nPR:N - READDIR on a guest/anonymous ksmbd share or AUTH_SYS NFS export needs no host account or capability. Automount of a malicious volume by udisks2/systemd also requires no attacker privileges on the victim.\nUI:N - Once the crafted or inline-data ext4 volume is exported or automounted, the attacker alone issues NFS/SMB READDIR or local getdents64. No separate victim must open a file or confirm a dialog at attack time.\nS:U - The out-of-bounds read and any resulting kernel crash stay within the host kernel\u0027s security authority. This is not a VM escape, IOMMU/DMA bypass, or other cross-boundary breakout.\nC:H - ext4_check_dir_entry over-reads de-\u003erec_len and adjacent dirent fields past the inline kmalloc buffer. If the inflated extra_size bound lets the check pass, dir_emit copies de-\u003ename for up to 255 bytes of adjacent kernel heap into the getdents/NFS/SMB reply.\nI:N - The defect is an over-read on the readdir path only. ext4_read_inline_dir does not write the over-read dirent, and there is no out-of-bounds write, type confusion, or control-flow hijack primitive.\nA:H - KASAN reports a slab-out-of-bounds read in __ext4_check_dir_entry. An over-read that reaches unmapped slab or guard pages oopses or panics the kernel, and the attacker can repeat READDIR/getdents against the crafted directory."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:39.655Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48"
        },
        {
          "url": "https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f"
        },
        {
          "url": "https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688"
        },
        {
          "url": "https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe"
        },
        {
          "url": "https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0"
        },
        {
          "url": "https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5"
        },
        {
          "url": "https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df"
        }
      ],
      "title": "ext4: fix out-of-bounds read in ext4_read_inline_dir()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89786",
    "datePublished": "2026-09-16T08:48:23.730Z",
    "dateReserved": "2026-09-11T19:38:34.766Z",
    "dateUpdated": "2026-10-19T08:52:39.655Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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