---
id: CVE-2026-31539
title: 'smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available

  The logic off managing recv credits by counting posted recv_io and
  granted credits is racy.

  That'…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 <
    e811e60e1cc79923c4388146eb1fa26a7482731e
  - >-
    Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 <
    f99996870222b598914a1f49d7375dc23752c237
  - >-
    Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 <
    6e3c5052f9686192e178806e017b7377155f4bab
  - Linux 6.18
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:10:46.426998Z'
published: '2026-04-24'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:15.186Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31539'
references:
  - url: 'https://git.kernel.org/stable/c/e811e60e1cc79923c4388146eb1fa26a7482731e'
  - url: 'https://git.kernel.org/stable/c/f99996870222b598914a1f49d7375dc23752c237'
  - url: 'https://git.kernel.org/stable/c/6e3c5052f9686192e178806e017b7377155f4bab'
tags:
  - cve.org
epss: 0.00426
epssPercentile: 0.35414
ingestedAt: '2026-10-16T17:24:46.660Z'
---

## Overview

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

smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available

The logic off managing recv credits by counting posted recv_io and
granted credits is racy.

That's because the peer might already consumed a credit,
but between receiving the incoming recv at the hardware
and processing the completion in the 'recv_done' functions
we likely have a window where we grant credits, which
don't really exist.

So we better have a decicated counter for the
available credits, which will be incremented
when we posted new recv buffers and drained when
we grant the credits to the peer.

## Affected

- `Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 < e811e60e1cc79923c4388146eb1fa26a7482731e`
- `Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 < f99996870222b598914a1f49d7375dc23752c237`
- `Linux >= 5fb9b459b3686e366640edd4e62805ef7b4de927 < 6e3c5052f9686192e178806e017b7377155f4bab`
- `Linux 6.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.