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

Description

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.

Timeline

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)

0.21% · top 89% of all CVEs (12 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

• Linux · Linux

  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < 4d20106c536b73c4a8a02652dc85e35898baebf7
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < 61a395967de06edba58760e81907a272db749faa
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < e94676a08af6312aa72d8a981232b281f9bcfcf5
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < d8c184bec24b5a00ae96d704856d935eaded1685
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < 3933884bc3102898b458c53fbd1ac52eb9cdb8a4
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < 83663c0b739480c00cfe785675db87520ec484ed
  • affected 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 – < c7e6b863d298f56522d0d08554bbea7f142e6588

• Linux · Linux

  • affected 5.13
  • unaffected < 5.13
  • unaffected 5.15.221 – ≤ 5.15.*
  • unaffected 6.1.188 – ≤ 6.1.*
  • unaffected 6.6.157 – ≤ 6.6.*
  • unaffected 6.12.110 – ≤ 6.12.*
  • unaffected 6.18.52 – ≤ 6.18.*
  • unaffected 7.2.6 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-80308 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-89787](https://cveledger.app/badge/CVE-2026-89787.svg)](https://cveledger.app/cve/CVE-2026-89787)

Record last updated 19 Oct 2026, 08:52 UTC.