---
id: CVE-2026-71217
title: A flaw was found in iperf3
summary: >-
  A flaw was found in iperf3. A remote attacker can exploit this vulnerability
  by sending crafted control-channel JSON with oversized numeric parameters,
  such as `parallel` and `len`, which are not properly validated by the server.
  This im…
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'
cwe:
  - CWE-20
published: '2026-08-11'
updated: '2026-08-31'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-71217'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:61257'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-71217'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2460984'
    label: secalert@redhat.com
  - url: >-
      https://github.com/esnet/iperf/commit/494dd377eca4689672becdf06a85158557db1586
    label: secalert@redhat.com
tags:
  - nvd
  - exploit-available
epss: 0.00824
epssPercentile: 0.55579
ingestedAt: '2026-08-31T09:05:50.037Z'
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/Reelix/CVE-2026-71217-PoC'
  checkedAt: '2026-09-26T09:05:57.768Z'
exploitAvailable: true
---

## Overview

A flaw was found in iperf3. A remote attacker can exploit this vulnerability by sending crafted control-channel JSON with oversized numeric parameters, such as `parallel` and `len`, which are not properly validated by the server. This improper input validation can lead to excessive stream and thread creation, as well as large buffer allocations, causing resource exhaustion. Consequently, this can result in a Denial of Service (DoS) on the affected iperf3 server.

## Remediation

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