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CVE-2026-64578

ksmbd: validate compound request size before reading StructureSize2 PUBLISHED

Description (CNA)

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 task kworker/0:1/14 The buggy address is located 172 bytes inside of allocated 173-byte region Workqueue: ksmbd-io handle_ksmbd_work Call Trace: ... kasan_report (mm/kasan/report.c:595) ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) handle_ksmbd_work (fs/smb/server/server.c:119) process_one_work (kernel/workqueue.c:3314) worker_thread (kernel/workqueue.c:3397) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) Reject any compound element that is too small to hold StructureSize2 before dereferencing it.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 415d0fff0451ad7ad4caa910f2bb0f562f0fd60f; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 1b6740525f5af90868d557c31b496ae689c8c549; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 2c307126ed8e7adddab82b8e31d962d3a2156ab1; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before f7550a91ab211726f59cb137523b7a9eae1ac6eb; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before f0e337e7db67cc1c832958bbb6c4026bdceacfdb; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before ea128f06d2fb2186f0cac0c9f3e953e4d1f5c29a; affected e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 before 15b38176fd1530372905c602fde51fe89ec8c877
Linux / Linuxaffected 5.15; unaffected 0 before 5.15; unaffected 5.15.216 through 5.15.*; unaffected 6.1.183 through 6.1.*; unaffected 6.6.148 through 6.6.*; unaffected 6.12.101 through 6.12.*; unaffected 6.18.42 through 6.18.*; unaffected 7.1.6 through 7.1.*; unaffected 7.2 through *

CWE

No CWE identifiers supplied.

References