# CVE-2026-64578: linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: validate compound request size before rea...

CVE-2026-64578 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-64578, released August 7, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-64578
- Priority: High
- CVSS: 8.2 (high)
- EPSS: 0.0034
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 5, 2026

## 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 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.187-1 | [DEBIAN-CVE-2026-64578](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64578.md) | Aug 7, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.101-1 | [DEBIAN-CVE-2026-64578](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64578.md) | Aug 7, 2026 |
| Linux | linux Debian 14 | 7.1.6-1 | [DEBIAN-CVE-2026-64578](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64578.md) | Aug 7, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.101-1~deb12u1 | [DEBIAN-CVE-2026-64578](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64578.md) | Aug 7, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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