---
id: CVE-2021-47001
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xprtrdma: Fix cwnd update ordering

  After a reconnect, the reply handler is opening the cwnd (and thus
  enabling more RPC Calls to be sent) /before/ rpcrdma_post_recvs()…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xprtrdma: Fix cwnd update ordering

  After a reconnect, the reply handler is opening the cwnd (and thus
  enabling more RPC Calls to be sent) /before/ rpcrdma_post_recvs()…
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'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.5, < 5.10.38'
  - 'linux_kernel >= 5.11, < 5.11.22'
  - 'linux_kernel >= 5.12, < 5.12.5'
patched:
  - linux_kernel 5.12.5
published: '2024-02-28'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-47001'
references:
  - url: 'https://git.kernel.org/stable/c/19b5fa9489b5706bc878c3a522a7f771079e2fa0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/35d8b10a25884050bb3b0149b62c3818ec59f77c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8834ecb5df22b7ff3c9b0deba7726579bb613f95'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/eddae8be7944096419c2ae29477a45f767d0fcd4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/19b5fa9489b5706bc878c3a522a7f771079e2fa0'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/35d8b10a25884050bb3b0149b62c3818ec59f77c'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/8834ecb5df22b7ff3c9b0deba7726579bb613f95'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/eddae8be7944096419c2ae29477a45f767d0fcd4'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://security.netapp.com/advisory/ntap-20250411-0001/'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00743
epssPercentile: 0.52782
ingestedAt: '2026-08-04T10:39:39.030Z'
---

## Overview

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

xprtrdma: Fix cwnd update ordering

After a reconnect, the reply handler is opening the cwnd (and thus
enabling more RPC Calls to be sent) /before/ rpcrdma_post_recvs()
can post enough Receive WRs to receive their replies. This causes an
RNR and the new connection is lost immediately.

The race is most clearly exposed when KASAN and disconnect injection
are enabled. This slows down rpcrdma_rep_create() enough to allow
the send side to post a bunch of RPC Calls before the Receive
completion handler can invoke ib_post_recv().

## Affected

- `linux_kernel >= 5.5, < 5.10.38`
- `linux_kernel >= 5.11, < 5.11.22`
- `linux_kernel >= 5.12, < 5.12.5`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.12.5`