CVE-2026-31704: Linux Kernel

Medium severity, CVSS 5.5. EPSS: 0.2% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: ksmbd: use check_add_overflow() to prevent u16 DACL size overflow set_posix_acl_entries_dacl() and set_ntacl_dacl() accumulate ACE sizes in u16 variables. When a file has many POSIX ACL entries, the accumulated size can wrap past 65535, causing the pointer arithmetic (char *)pndace + *size to land within already-written ACEs. Subsequent writes then overwrite earlier entries, and pndacl->size gets a truncated value. Use check_add_overflow() at each accumulation point to detect the wrap before it corrupts the buffer, consistent with existing check_mul_overflow() usage elsewhere in smbacl.c.

Affected products

• Linux Linux Kernel: from 5.15, before 6.6.136 (fixed in 6.6.136); from 6.7, before 6.12.84 (fixed in 6.12.84); from 6.13, before 6.18.25 (fixed in 6.18.25); from 6.19, before 7.0.2 (fixed in 7.0.2)

Published 2026-05-01. Last modified 2026-06-17.