Vulnerability-Lookup

CVE-2026-89787 (GCVE-0-2026-89787)

Vulnerability from cvelistv5 – Published: 2026-09-16 08:48 – Updated: 2026-09-16 08:48

Title

ext4: check dir entry fits before reading the hash trailer in ext4_search_dir()

Summary

In the Linux kernel, the following vulnerability has been resolved: ext4: check dir entry fits before reading the hash trailer in ext4_search_dir() For casefolded encrypted directories ext4 stores an 8-byte hash trailer after the name (EXT4_DIRENT_HASHES()), at an offset derived from de->name_len. On the sb_no_casefold_compat_fallback() path ext4_match() reads that trailer, but ext4_search_dir()'s by-hand pre-check only tests de->name + de->name_len <= dlimit, which proves the name fits, not the rounded trailer. A crafted entry whose name ends at the block boundary passes the check while EXT4_DIRENT_HASHES(de) lands past the block end, so ext4_match() reads out of bounds on an ordinary lookup. KASAN reports it as a use-after-free when the page after the directory block holds a freed object: BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435) Read of size 4 at addr ffff888010458000 by task exploit Call Trace: ext4_match (fs/ext4/namei.c:1435) ext4_search_dir (fs/ext4/namei.c:1470) __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632) ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769) ... filename_lookup (fs/namei.c:2842) vfs_statx (fs/stat.c:353) __do_sys_newfstatat (fs/stat.c:538) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Require, for hash-in-dirent directories, that the whole entry including the rounded trailer fits before calling ext4_match(). This is the same bound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so no well-formed entry is rejected. The other caller, ext4_find_dest_de(), runs ext4_check_dir_entry() first and is unaffected.

Severity

No CVSS data available.

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/4d20106c536b73c4a…
https://git.kernel.org/stable/c/61a395967de06edba…
https://git.kernel.org/stable/c/e94676a08af6312aa…
https://git.kernel.org/stable/c/d8c184bec24b5a00a…
https://git.kernel.org/stable/c/3933884bc3102898b…
https://git.kernel.org/stable/c/83663c0b739480c00…
https://git.kernel.org/stable/c/c7e6b863d298f5652…

Impacted products

2 products

Vendor	Product	Version	CPE status
Linux	Linux	Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < 4d20106c536b73c4a8a02652dc85e35898baebf7 (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < 61a395967de06edba58760e81907a272db749faa (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < e94676a08af6312aa72d8a981232b281f9bcfcf5 (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < d8c184bec24b5a00ae96d704856d935eaded1685 (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < 3933884bc3102898b458c53fbd1ac52eb9cdb8a4 (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < 83663c0b739480c00cfe785675db87520ec484ed (git) Affected: 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 , < c7e6b863d298f56522d0d08554bbea7f142e6588 (git)	guessed
Linux	Linux	Affected: 5.13 Unaffected: 0 , < 5.13 (semver) Unaffected: 5.15.221 , ≤ 5.15.* (semver) Unaffected: 6.1.188 , ≤ 6.1.* (semver) Unaffected: 6.6.157 , ≤ 6.6.* (semver) Unaffected: 6.12.110 , ≤ 6.12.* (semver) Unaffected: 6.18.52 , ≤ 6.18.* (semver) Unaffected: 7.2.6 , ≤ 7.2.* (semver) Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)	guessed

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/namei.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "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-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.221",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "5.13",
                  "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\next4: check dir entry fits before reading the hash trailer in ext4_search_dir()\n\nFor casefolded encrypted directories ext4 stores an 8-byte hash trailer\nafter the name (EXT4_DIRENT_HASHES()), at an offset derived from\nde-\u003ename_len.  On the sb_no_casefold_compat_fallback() path ext4_match()\nreads that trailer, but ext4_search_dir()\u0027s by-hand pre-check only tests\nde-\u003ename + de-\u003ename_len \u003c= dlimit, which proves the name fits, not the\nrounded trailer.  A crafted entry whose name ends at the block boundary\npasses the check while EXT4_DIRENT_HASHES(de) lands past the block end,\nso ext4_match() reads out of bounds on an ordinary lookup.  KASAN reports\nit as a use-after-free when the page after the directory block holds a\nfreed object:\n\n  BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435)\n  Read of size 4 at addr ffff888010458000 by task exploit\n  Call Trace:\n   ext4_match (fs/ext4/namei.c:1435)\n   ext4_search_dir (fs/ext4/namei.c:1470)\n   __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632)\n   ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769)\n   ...\n   filename_lookup (fs/namei.c:2842)\n   vfs_statx (fs/stat.c:353)\n   __do_sys_newfstatat (fs/stat.c:538)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n\nRequire, for hash-in-dirent directories, that the whole entry including\nthe rounded trailer fits before calling ext4_match().  This is the same\nbound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so\nno well-formed entry is rejected.  The other caller, ext4_find_dest_de(),\nruns ext4_check_dir_entry() first and is unaffected."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-16T08:48:24.403Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7"
        },
        {
          "url": "https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa"
        },
        {
          "url": "https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5"
        },
        {
          "url": "https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685"
        },
        {
          "url": "https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4"
        },
        {
          "url": "https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed"
        },
        {
          "url": "https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588"
        }
      ],
      "title": "ext4: check dir entry fits before reading the hash trailer in ext4_search_dir()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89787",
    "datePublished": "2026-09-16T08:48:24.403Z",
    "dateReserved": "2026-09-11T19:38:34.766Z",
    "dateUpdated": "2026-09-16T08:48:24.403Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-89787",
      "date": "2026-09-16",
      "epss": "0.00205",
      "percentile": "0.10809"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-89787\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-09-16T09:17:09.460\",\"lastModified\":\"2026-09-16T09:17:09.460\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\next4: check dir entry fits before reading the hash trailer in ext4_search_dir()\\n\\nFor casefolded encrypted directories ext4 stores an 8-byte hash trailer\\nafter the name (EXT4_DIRENT_HASHES()), at an offset derived from\\nde-\u003ename_len.  On the sb_no_casefold_compat_fallback() path ext4_match()\\nreads that trailer, but ext4_search_dir()\u0027s by-hand pre-check only tests\\nde-\u003ename + de-\u003ename_len \u003c= dlimit, which proves the name fits, not the\\nrounded trailer.  A crafted entry whose name ends at the block boundary\\npasses the check while EXT4_DIRENT_HASHES(de) lands past the block end,\\nso ext4_match() reads out of bounds on an ordinary lookup.  KASAN reports\\nit as a use-after-free when the page after the directory block holds a\\nfreed object:\\n\\n  BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435)\\n  Read of size 4 at addr ffff888010458000 by task exploit\\n  Call Trace:\\n   ext4_match (fs/ext4/namei.c:1435)\\n   ext4_search_dir (fs/ext4/namei.c:1470)\\n   __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632)\\n   ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769)\\n   ...\\n   filename_lookup (fs/namei.c:2842)\\n   vfs_statx (fs/stat.c:353)\\n   __do_sys_newfstatat (fs/stat.c:538)\\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\\n\\nRequire, for hash-in-dirent directories, that the whole entry including\\nthe rounded trailer fits before calling ext4_match().  This is the same\\nbound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so\\nno well-formed entry is rejected.  The other caller, ext4_find_dest_de(),\\nruns ext4_check_dir_entry() first and is unaffected.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/ext4/namei.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"4d20106c536b73c4a8a02652dc85e35898baebf7\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"61a395967de06edba58760e81907a272db749faa\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"e94676a08af6312aa72d8a981232b281f9bcfcf5\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"d8c184bec24b5a00ae96d704856d935eaded1685\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"3933884bc3102898b458c53fbd1ac52eb9cdb8a4\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"83663c0b739480c00cfe785675db87520ec484ed\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"471fbbea7ff7061b2d6474665cb5a2ceb4fd6500\",\"lessThan\":\"c7e6b863d298f56522d0d08554bbea7f142e6588\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/ext4/namei.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.13\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.13\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.221\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.188\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.157\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.110\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.52\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2.6\",\"lessThanOrEqual\":\"7.2.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.3-rc1\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}

FKIE_CVE-2026-89787

Vulnerability from fkie_nvd - Published: 2026-09-16 09:17 - Updated: 2026-09-16 09:17

Severity

Summary

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/namei.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "4d20106c536b73c4a8a02652dc85e35898baebf7",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "61a395967de06edba58760e81907a272db749faa",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "e94676a08af6312aa72d8a981232b281f9bcfcf5",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "d8c184bec24b5a00ae96d704856d935eaded1685",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "3933884bc3102898b458c53fbd1ac52eb9cdb8a4",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "83663c0b739480c00cfe785675db87520ec484ed",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            },
            {
              "lessThan": "c7e6b863d298f56522d0d08554bbea7f142e6588",
              "status": "affected",
              "version": "471fbbea7ff7061b2d6474665cb5a2ceb4fd6500",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/ext4/namei.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "lessThan": "5.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "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-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: check dir entry fits before reading the hash trailer in ext4_search_dir()\n\nFor casefolded encrypted directories ext4 stores an 8-byte hash trailer\nafter the name (EXT4_DIRENT_HASHES()), at an offset derived from\nde-\u003ename_len.  On the sb_no_casefold_compat_fallback() path ext4_match()\nreads that trailer, but ext4_search_dir()\u0027s by-hand pre-check only tests\nde-\u003ename + de-\u003ename_len \u003c= dlimit, which proves the name fits, not the\nrounded trailer.  A crafted entry whose name ends at the block boundary\npasses the check while EXT4_DIRENT_HASHES(de) lands past the block end,\nso ext4_match() reads out of bounds on an ordinary lookup.  KASAN reports\nit as a use-after-free when the page after the directory block holds a\nfreed object:\n\n  BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435)\n  Read of size 4 at addr ffff888010458000 by task exploit\n  Call Trace:\n   ext4_match (fs/ext4/namei.c:1435)\n   ext4_search_dir (fs/ext4/namei.c:1470)\n   __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632)\n   ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769)\n   ...\n   filename_lookup (fs/namei.c:2842)\n   vfs_statx (fs/stat.c:353)\n   __do_sys_newfstatat (fs/stat.c:538)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n\nRequire, for hash-in-dirent directories, that the whole entry including\nthe rounded trailer fits before calling ext4_match().  This is the same\nbound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so\nno well-formed entry is rejected.  The other caller, ext4_find_dest_de(),\nruns ext4_check_dir_entry() first and is unaffected."
    }
  ],
  "id": "CVE-2026-89787",
  "lastModified": "2026-09-16T09:17:09.460",
  "metrics": {},
  "published": "2026-09-16T09:17:09.460",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

GHSA-CXFP-66MH-JHVV

Vulnerability from github – Published: 2026-09-16 09:30 – Updated: 2026-09-16 09:30

Details

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

ext4: check dir entry fits before reading the hash trailer in ext4_search_dir()

For casefolded encrypted directories ext4 stores an 8-byte hash trailer after the name (EXT4_DIRENT_HASHES()), at an offset derived from de->name_len. On the sb_no_casefold_compat_fallback() path ext4_match() reads that trailer, but ext4_search_dir()'s by-hand pre-check only tests de->name + de->name_len <= dlimit, which proves the name fits, not the rounded trailer. A crafted entry whose name ends at the block boundary passes the check while EXT4_DIRENT_HASHES(de) lands past the block end, so ext4_match() reads out of bounds on an ordinary lookup. KASAN reports it as a use-after-free when the page after the directory block holds a freed object:

BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435) Read of size 4 at addr ffff888010458000 by task exploit Call Trace: ext4_match (fs/ext4/namei.c:1435) ext4_search_dir (fs/ext4/namei.c:1470) __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632) ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769) ... filename_lookup (fs/namei.c:2842) vfs_statx (fs/stat.c:353) __do_sys_newfstatat (fs/stat.c:538) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Require, for hash-in-dirent directories, that the whole entry including the rounded trailer fits before calling ext4_match(). This is the same bound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so no well-formed entry is rejected. The other caller, ext4_find_dest_de(), runs ext4_check_dir_entry() first and is unaffected.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89787"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T09:17:09Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: check dir entry fits before reading the hash trailer in ext4_search_dir()\n\nFor casefolded encrypted directories ext4 stores an 8-byte hash trailer\nafter the name (EXT4_DIRENT_HASHES()), at an offset derived from\nde-\u003ename_len.  On the sb_no_casefold_compat_fallback() path ext4_match()\nreads that trailer, but ext4_search_dir()\u0027s by-hand pre-check only tests\nde-\u003ename + de-\u003ename_len \u003c= dlimit, which proves the name fits, not the\nrounded trailer.  A crafted entry whose name ends at the block boundary\npasses the check while EXT4_DIRENT_HASHES(de) lands past the block end,\nso ext4_match() reads out of bounds on an ordinary lookup.  KASAN reports\nit as a use-after-free when the page after the directory block holds a\nfreed object:\n\n  BUG: KASAN: use-after-free in ext4_match (fs/ext4/namei.c:1435)\n  Read of size 4 at addr ffff888010458000 by task exploit\n  Call Trace:\n   ext4_match (fs/ext4/namei.c:1435)\n   ext4_search_dir (fs/ext4/namei.c:1470)\n   __ext4_find_entry (fs/ext4/namei.c:1268 fs/ext4/namei.c:1632)\n   ext4_lookup (fs/ext4/namei.c:1703 fs/ext4/namei.c:1769)\n   ...\n   filename_lookup (fs/namei.c:2842)\n   vfs_statx (fs/stat.c:353)\n   __do_sys_newfstatat (fs/stat.c:538)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n\nRequire, for hash-in-dirent directories, that the whole entry including\nthe rounded trailer fits before calling ext4_match().  This is the same\nbound ext4_check_dir_entry() already enforces via ext4_dir_rec_len(), so\nno well-formed entry is rejected.  The other caller, ext4_find_dest_de(),\nruns ext4_check_dir_entry() first and is unaffected.",
  "id": "GHSA-cxfp-66mh-jhvv",
  "modified": "2026-09-16T09:30:30Z",
  "published": "2026-09-16T09:30:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89787"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3933884bc3102898b458c53fbd1ac52eb9cdb8a4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4d20106c536b73c4a8a02652dc85e35898baebf7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/61a395967de06edba58760e81907a272db749faa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/83663c0b739480c00cfe785675db87520ec484ed"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c7e6b863d298f56522d0d08554bbea7f142e6588"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d8c184bec24b5a00ae96d704856d935eaded1685"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e94676a08af6312aa72d8a981232b281f9bcfcf5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Action not permitted

CVE-2026-89787 (GCVE-0-2026-89787)

FKIE_CVE-2026-89787

GHSA-CXFP-66MH-JHVV

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