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

Type: advisorySource: Official CVE List1 source record

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_e

Announced Source revision 1
Original source ↗

CVE-2026-89787

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-89787

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "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"
      }
    ],
    "programFiles": [
      "fs/ext4/namei.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.13"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.13",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.15.221",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.188",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.157",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.110",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.52",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.2.6",
        "versionType": "semver",
        "lessThanOrEqual": "7.2.*"
      },
      {
        "status": "unaffected",
        "version": "7.3",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "fs/ext4/namei.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-89787

Source reference: /cveMetadata/cveId

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Event
#36257 · Revision 1
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