CVE-2026-89787

CVE CVE-2026-89787EUVD EUVD-2026-80308Published 2026-09-16T08:48:24.000Z

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <4d20106c536b73c4a8a02652dc85e35898baebf7; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <61a395967de06edba58760e81907a272db749faa; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <d8c184bec24b5a00ae96d704856d935eaded1685; patch: 6.6.157; patch: 6.1.188; 5.13; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <e94676a08af6312aa72d8a981232b281f9bcfcf5; patch: 0; patch: 6.12.110; patch: 7.2.6; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <3933884bc3102898b458c53fbd1ac52eb9cdb8a4; patch: 5.15.221; patch: 7.3-rc1; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <83663c0b739480c00cfe785675db87520ec484ed; 471fbbea7ff7061b2d6474665cb5a2ceb4fd6500 <c7e6b863d298f56522d0d08554bbea7f142e6588; patch: 6.18.52

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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