CVE-2026-31705

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment smb2_get_ea() applies 4-byte alignment padding via memset() after writing each EA entry. The bounds check on buf_free_len is performed before the value memcpy, but the alignment memset fires unconditionally afterward with no check on remaining space. When the EA value exactly fills the remaining buffer (buf_free_len == 0 after value subtraction), the alignment memset writes 1-3 NUL bytes past the buf_free_len boundary. In compound requests where the response buffer is shared across commands, the first command (e.g., READ) can consume most of the buffer, leaving a tight remainder for the QUERY_INFO EA response. The alignment memset then overwrites past the physical kvmalloc allocation into adjacent kernel heap memory. Add a bounds check before the alignment memset to ensure buf_free_len can accommodate the padding bytes. This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix potencial OOB in get_file_all_info() for compound requests") and commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound requests"), both of which added bounds checks before unconditional writes in QUERY_INFO response handlers.

Gravité et risque d'exploitation

CVE-2026-31705 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.40 %, ce qui la place devant 32.5 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 7.0.2, <=6.1.*, <=7.0.*, <=6.12.*, 6.1.71, f2283680a80571ca82d710bc6ecd8f8beac67d63, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, 0, <98f3de6ef4efbd899348d333f0902dc4ff14380c, 6.18.25, <6.6, <ddbbc8b2a09dd2cfed90871313e3691ae1db08a2, 5.15.145, <=6.6.*, 6.1.175, 6.6.136, <30010c952077a1c89ecdd71fc4d574c75a8f5617, 9f297df20d93411c0b4ddad7f88ba04a7cd36e77, 6.6, 6.12.84, <5.16, 7.1, <=6.18.*, <ffbce350c6fd1e99116ea57383b9031717e36d3b, <=*, <922d48fe8c19f388ffa2f709f33acaae4e408de2, <6.1.175, <790304c02bf9bd7b8171feda4294d6e62d32ae8f) 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/ddbbc8b2a09dd2cfed90871313e3691ae1db08a2
• https://git.kernel.org/stable/c/ffbce350c6fd1e99116ea57383b9031717e36d3b
• https://git.kernel.org/stable/c/98f3de6ef4efbd899348d333f0902dc4ff14380c
• https://git.kernel.org/stable/c/790304c02bf9bd7b8171feda4294d6e62d32ae8f
• https://git.kernel.org/stable/c/922d48fe8c19f388ffa2f709f33acaae4e408de2
• https://git.kernel.org/stable/c/30010c952077a1c89ecdd71fc4d574c75a8f5617