CVE-2026-31704

ksmbd: use check_add_overflow() to prevent u16 DACL size overflow

Published May 1, 2026 CVSS 3.1 · 5.5 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4665-1 linux security update
Debian DLA Debian DLA DLA-4671-1 linux-6.1 security update
Ubuntu USN Ubuntu USN USN-8488-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8488-2 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-8507-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8567-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8569-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-8574-1 Linux kernel (GCP FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8574-2 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8595-1 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8596-1 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8595-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8603-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8606-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8607-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8608-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8609-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8574-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8595-3 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8619-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-8665-1 Linux kernel (Raspberry Pi) vulnerabilities
History
Type Values Removed Values Added
Weaknesses NVD-CWE-noinfo
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Description 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.
Title ksmbd: use check_add_overflow() to prevent u16 DACL size overflow
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 15, 2026, 1:18 AM
Reserved
Mar 9, 2026, 3:48 PM
Status
Modified
Published
May 1, 2026, 2:16 PM
Modified
Nov 11, 2026, 9:10 PM
Severity
Public date
May 1, 2026, 12:00 AM