CVE-2026-89492 (GCVE-0-2026-89492)
Vulnerability from cvelistv5
Published
2026-09-11 19:43
Modified
2026-10-21 12:47
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate directory-index entry counts when reading metadata ocfs2_validate_dx_leaf() and ocfs2_validate_dx_root() check the ECC and signature of an indexed-directory block before it reaches higher-level callers, but neither validator bounds the ocfs2_dx_entry_list counts against the capacity of the block that holds them. ocfs2_dx_dir_search() then walks for (i = 0; i < le16_to_cpu(entry_list->de_num_used); i++) dx_entry = &entry_list->de_entries[i]; over de_num_used entries with no bounds check. entry_list is either dx_leaf->dl_list (from ocfs2_read_dx_leaf) or, for an inline root, dx_root->dr_entries. A crafted on-disk image can set de_num_used (and de_count, which is the __counted_by_le() bound of de_entries) to 0xffff and make the walk read far past the end of the 4KB metadata block, giving a slab out-of-bounds read reachable from any path lookup, stat() or open() on an indexed directory once the image is mounted. Commit 775c17386a6f ("ocfs2: validate dx_root extent list fields during block read") already bounds dr_list for the non-inline dx_root, but left the inline dr_entries path and the dx_leaf dl_list unchecked. Add the same read-time validation for both entry lists: de_count must equal the capacity of the block (ocfs2_dx_entries_per_leaf()/per_root()) and de_num_used must not exceed de_count, rejecting corrupted metadata with -EFSCORRUPTED before ocfs2_dx_dir_search() can walk an out-of-range entry array. de_count is always written as exactly the block capacity when a leaf or inline root is formatted, so the equality check does not reject any valid image. Found by 0sec automated security-research tooling (https://0sec.ai).
References
Impacted products
Vendor Product Version
Linux Linux Version: 9b7895efac906d66d19856194e1ba61f37e231a4
Version: 9b7895efac906d66d19856194e1ba61f37e231a4
Version: 9b7895efac906d66d19856194e1ba61f37e231a4
Version: 9b7895efac906d66d19856194e1ba61f37e231a4
Version: 9b7895efac906d66d19856194e1ba61f37e231a4
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ocfs2/dir.c"
          ],
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          "programFiles": [
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          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "2.6.30"
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.12.111",
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            {
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              "status": "unaffected",
              "version": "6.18.51",
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            },
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              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.160",
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                  "vulnerable": true
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: validate directory-index entry counts when reading metadata\n\nocfs2_validate_dx_leaf() and ocfs2_validate_dx_root() check the ECC and\nsignature of an indexed-directory block before it reaches higher-level\ncallers, but neither validator bounds the ocfs2_dx_entry_list counts\nagainst the capacity of the block that holds them.\n\nocfs2_dx_dir_search() then walks\n\n\tfor (i = 0; i \u003c le16_to_cpu(entry_list-\u003ede_num_used); i++)\n\t\tdx_entry = \u0026entry_list-\u003ede_entries[i];\n\nover de_num_used entries with no bounds check.  entry_list is either\ndx_leaf-\u003edl_list (from ocfs2_read_dx_leaf) or, for an inline root,\ndx_root-\u003edr_entries.  A crafted on-disk image can set de_num_used (and\nde_count, which is the __counted_by_le() bound of de_entries) to 0xffff\nand make the walk read far past the end of the 4KB metadata block, giving\na slab out-of-bounds read reachable from any path lookup, stat() or open()\non an indexed directory once the image is mounted.\n\nCommit 775c17386a6f (\"ocfs2: validate dx_root extent list fields during\nblock read\") already bounds dr_list for the non-inline dx_root, but left\nthe inline dr_entries path and the dx_leaf dl_list unchecked.  Add the\nsame read-time validation for both entry lists: de_count must equal the\ncapacity of the block (ocfs2_dx_entries_per_leaf()/per_root()) and\nde_num_used must not exceed de_count, rejecting corrupted metadata with\n-EFSCORRUPTED before ocfs2_dx_dir_search() can walk an out-of-range entry\narray.\n\nde_count is always written as exactly the block capacity when a leaf or\ninline root is formatted, so the equality check does not reject any valid\nimage.\n\nFound by 0sec automated security-research tooling (https://0sec.ai)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - OCFS2 sets s_export_op to ocfs2_export_ops and is commonly NFS-exported on shared cluster LUNs; remote nfsd LOOKUP/GETATTR/CREATE reach ocfs2_lookup\u2192ocfs2_find_entry_dx\u2192ocfs2_dx_dir_search (and create\u2192ocfs2_dx_entry_list_insert) over the network with no local syscall on the server.\nAC:L - The attacker fully controls on-disk de_num_used and de_count in a dx_root or dx_leaf; inflating them above the fixed 4K-block capacity (e.g. 0xffff with de_num_used still below de_count) deterministically overflows the entry walk and insert with no race or attacker-uncontrollable layout.\nPR:N - Triggering needs only NFS LOOKUP or CREATE on an exported directory, including guest or anonymous NFS, or any unprivileged accessor of a mounted volume holding the forged index; planting malformed directory-index metadata on shared cluster storage does not require init-namespace root on the victim.\nUI:N - Once the OCFS2 volume is mounted and NFS-exported as a normal cluster or NAS deployment, the attacker triggers the overflow by their own LOOKUP, stat, open, or CREATE; no additional victim action such as mounting an image or opening a file is required.\nS:U - The overflow corrupts kernel memory and OCFS2 metadata on the host that parses the forged directory index; it does not escape a VM, bypass an IOMMU, or otherwise cross into a separate security authority.\nC:H - ocfs2_dx_dir_search walks de_num_used with no capacity check, so de_num_used of 0xffff reads far past the 4KB metadata block (up to about 1 MiB of adjacent kernel memory), an unbounded out-of-bounds read that enables high-impact disclosure.\nI:H - When de_count is inflated past block capacity and de_num_used is still less than de_count, create/mkdir calls ocfs2_dx_entry_list_insert and writes a dx_entry at de_entries[de_num_used] past the block; unlink memmove is similarly unbounded, yielding an attacker-triggered kernel out-of-bounds write.\nA:H - The unbounded out-of-bounds read on lookup and out-of-bounds write on create against kernel metadata buffers cause a kernel oops or panic, fully denying availability of the OCFS2 node until reboot."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:47:37.117Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/aad3129b8e915d0ff492bb7517d825d8490cfdd9"
        },
        {
          "url": "https://git.kernel.org/stable/c/5e661f55ca8568471fce558effe81cca112f5cb2"
        },
        {
          "url": "https://git.kernel.org/stable/c/fcfcba8fe17dbf2c8805690b8cc25e32d81249a4"
        },
        {
          "url": "https://git.kernel.org/stable/c/b8a5c0c32df2c5b685ceef76ac77e37c7e1dc3ed"
        },
        {
          "url": "https://git.kernel.org/stable/c/bc70726ddad53c7e9a9a85915bf2415b0d4f42f9"
        }
      ],
      "title": "ocfs2: validate directory-index entry counts when reading metadata",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89492",
    "datePublished": "2026-09-11T19:43:44.137Z",
    "dateReserved": "2026-09-11T19:38:34.713Z",
    "dateUpdated": "2026-10-21T12:47:37.117Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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