# CVE-2026-74521: linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: use memcmp() to compare ClientGUIDs  Clie...

CVE-2026-74521 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-74521, released August 16, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-74521
- Priority: Urgent
- CVSS: 9.1 (critical)
- EPSS: 0.0041
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 15, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:  ksmbd: use memcmp() to compare ClientGUIDs  ClientGUID is a fixed-size binary value and can contain embedded NUL bytes. strncmp() stops comparing at the first NUL byte, so different ClientGUID values can incorrectly be treated as equal.  Use memcmp() in SMB3 multichannel session binding and FSCTL_VALIDATE_NEGOTIATE_INFO to compare all SMB2_CLIENT_GUID_SIZE bytes.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.190-1 | [DEBIAN-CVE-2026-74521](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74521.md) | Aug 16, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-74521](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74521.md) | Aug 16, 2026 |
| Linux | linux Debian 14 | 7.1.8-1 | [DEBIAN-CVE-2026-74521](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74521.md) | Aug 16, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-74521](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74521.md) | Aug 16, 2026 |

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Data as of 2026-11-09T19:38:12Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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