CVE-2026-64578

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: validate compound request size before reading StructureSize2

When ksmbd validates a compound (chained) SMB2 request,

ksmbd_smb2_check_message() reads pdu->StructureSize2 without first

checking that the compound element is large enough to contain it.

StructureSize2 is a 2-byte field at offset 64

(__SMB2_HEADER_STRUCTURE_SIZE) from the start of each element.

The compound-walking logic only guarantees that a full 64-byte SMB2

header is present for the trailing element: when NextCommand is 0, len is

reduced to the number of bytes remaining after next_smb2_rcv_hdr_off. A

remote client can craft a compound request whose last element has exactly

64 bytes, so the 2-byte StructureSize2 read at offset 64 extends one byte

past the receive buffer, producing a slab-out-of-bounds read.

BUG: KASAN: slab-out-of-bounds in ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402)

Read of size 2 at addr ffff888012ae31ac by t

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References