---
id: CVE-2026-11586
title: 'By default, curl automatically responds to WebSocket PING frames'
summary: |-
  By default, curl automatically responds to WebSocket PING frames. Because curl
  lacks an upper bound on memory allocation for unacknowledged frames, a
  malicious server can exhaust all available memory by flooding curl with rapid,
  sequenti…
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-770
vendor: haxx
product: curl
affected:
  - 'curl >= 8.16.0, < 8.21.0'
patched:
  - curl 8.21.0
published: '2026-07-03'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:25.700'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11586'
references:
  - url: 'https://curl.se/docs/CVE-2026-11586.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-11586.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3788931'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-07-06T15:16:22.568075Z'
epss: 0.00609
epssPercentile: 0.4682
ingestedAt: '2026-07-04T04:55:39.424Z'
---

## Overview

By default, curl automatically responds to WebSocket PING frames. Because curl
lacks an upper bound on memory allocation for unacknowledged frames, a
malicious server can exhaust all available memory by flooding curl with rapid,
sequential PING messages.

## Affected

- `curl >= 8.16.0, < 8.21.0`

## Remediation

Upgrade past the affected range:

- `curl 8.21.0`