---
id: CVE-2026-11352
title: |-
  An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server
  to trigger a remote denial of service against a curl or libcurl client.
  Because the helper function discards zero-length UDP datagrams before counting
  them tow…
summary: |-
  An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server
  to trigger a remote denial of service against a curl or libcurl client.
  Because the helper function discards zero-length UDP datagrams before counting
  them tow…
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-835
vendor: haxx
product: curl
affected:
  - 'curl >= 8.18.0, < 8.21.0'
patched:
  - curl 8.21.0
published: '2026-07-03'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T07:16:25.353'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-11352'
references:
  - url: 'https://curl.se/docs/CVE-2026-11352.html'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://curl.se/docs/CVE-2026-11352.json'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3783438'
    label: 2499f714-1537-4658-8207-48ae4bb9eae9
  - url: 'https://hackerone.com/reports/3783438'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-07-06T18:26:03.249042Z'
epss: 0.00715
epssPercentile: 0.5187
ingestedAt: '2026-07-04T04:55:39.411Z'
---

## Overview

An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server
to trigger a remote denial of service against a curl or libcurl client.
Because the helper function discards zero-length UDP datagrams before counting
them toward the per-call packet budget, a connected QUIC peer can continuously
stream empty datagrams to indefinitely stall the client.

## Affected

- `curl >= 8.18.0, < 8.21.0`

## Remediation

Upgrade past the affected range:

- `curl 8.21.0`