---
id: CVE-2026-101276
title: >-
  iperf3 3.21 (esnet/iperf) contains a remote, unauthenticated heap
  use-after-free: the server's per-test watchdog server_timer_proc() frees
  streams without cancelling/joining their worker threads, so a blocked worker
  dereferences a freed …
summary: >-
  iperf3 3.21 (esnet/iperf) contains a remote, unauthenticated heap
  use-after-free: the server's per-test watchdog server_timer_proc() frees
  streams without cancelling/joining their worker threads, so a blocked worker
  dereferences a freed …
severity: critical
cvss: 9.2
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-416
vendor: esnet
product: iperf3
affected:
  - iperf3 3.21
published: '2026-09-30'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T21:16:54.913'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-101276'
references:
  - url: 'https://newreleases.io/project/github/esnet/iperf/release/3.22'
    label: 98a01053-8a31-4f6d-9aa9-252be161adc6
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-30T21:25:07.818Z'
---

## Overview

iperf3 3.21 (esnet/iperf) contains a remote, unauthenticated heap use-after-free: the server's per-test watchdog server_timer_proc() frees streams without cancelling/joining their worker threads, so a blocked worker dereferences a freed iperf_stream; fixed in 3.22.

## Remediation

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