CVE-2026-89786

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix out-of-bounds read in ext4_read_inline_dir() ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64(): BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry Read of size 2 at addr ffff88800f3dd23c by task exploit/148 ... __ext4_check_dir_entry ext4_read_inline_dir iterate_dir The dirent payload lives in a buffer of exactly inline_size bytes: dir_buf = kmalloc(inline_size, GFP_NOFS); but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets. A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected. Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.

Gravité et risque d'exploitation

CVE-2026-89786 obtient un score CVSS de 9.1/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.70 %, ce qui la place devant 51.8 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <6702c7da86d8cdb88d0fc57166286e115ffeb8c0, <=6.12.*, <1a1dea633b724a1c042dbcdb1fed27f410916688, 5.15.221, 0, 6.1.188, 6.18.52, 7.3-rc1, <36bf17bb90cdf7a623499b624b05acde4d2feef5, <3.10, <=6.6.*, 6.6.157, <b060861f662d4826dc700a1c3584243bb3474cfe, 7.2.6, c4d8b0235aa98f8c26bf94d308be3fdd24154572, <=6.18.*, <5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f, 6.12.110, <=7.2.*, <9333cc809f0a89e001b814155a6cb8903a6274df, <=*, <=5.15.*, 3.10, <d1e7c186555ad65554fd2f2b02f5a539aa35ae48) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48
• https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f
• https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688
• https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe
• https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0
• https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5
• https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df