Linux Kernel KSMBD SMB Direct Integer Underflow Remote Code Execution Vulnerability

November 13th, 2026
ZDI-26-998 ZDI-CAN-33549

CVE ID

CVSS Score

9.0 AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected Vendors

Linux

Affected Products

Kernel KSMBD

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Linux Kernel KSMBD. Authentication may or may not be required to exploit this vulnerability, depending upon configuration. Only systems with SMB Direct enabled are vulnerable.

The specific flaw exists within the smbdirect_connection_rdma_xmit function. The issue results from the lack of proper validation of user-supplied data, which can result in an integer underflow before writing to memory. An attacker can leverage this vulnerability to execute code in the context of the kernel.

Additional Details

Linux has issued an update to correct this vulnerability. More details can be found at:
https://github.com/torvalds/linux/commit/7193241a49c958782ba4b8df06da3734d1e317d2

Disclosure Timeline

  • 2026-10-21 - Vulnerability reported to vendor
  • 2026-11-13 - Coordinated public release of advisory
  • 2026-11-13 - Advisory Updated

Credit

HYEONTAE LEE

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