---
id: CVE-2024-3651
aliases:
  - GHSA-jjg7-2v4v-x38h
  - PYSEC-2024-60
title: >-
  Internationalized Domain Names in Applications (IDNA) vulnerable to denial of
  service from specially crafted inputs to idna.encode
summary: >-
  Internationalized Domain Names in Applications (IDNA) vulnerable to denial of
  service from specially crafted inputs to idna.encode
severity: medium
cvss: 6.2
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: idna
product: idna
ecosystem: pip
affected:
  - idna < 3.7
patched:
  - idna 3.7
published: '2024-04-11'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:12.774088619Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-jjg7-2v4v-x38h'
references:
  - url: 'https://github.com/kjd/idna/security/advisories/GHSA-jjg7-2v4v-x38h'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2024-3651'
  - url: >-
      https://github.com/kjd/idna/commit/1d365e17e10d72d0b7876316fc7b9ca0eebdd38d
  - url: 'https://github.com/kjd/idna'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/idna/PYSEC-2024-60.yaml
  - url: 'https://huntr.com/bounties/93d78d07-d791-4b39-a845-cbfabc44aadb'
  - url: 'https://lists.debian.org/debian-lts-announce/2024/05/msg00006.html'
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4YQUPYH3SVZ5GFF2CDQ55FCM575AZTF2
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/F2S5E23N6E52S46KGNYTDFB75LOC4N4D
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/S5IDLLD2IKSIVRBSLB34WTSYGLMWUFWF
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ULSC7HBJKXB3BZV367WM5BR6DFEC4Z43
tags:
  - osv
  - pip
epss: 0.01386
epssPercentile: 0.71019
ingestedAt: '2026-09-12T03:13:01.706Z'
---

## Overview

### Impact
A specially crafted argument to the `idna.encode()` function could consume significant resources. This may lead to a denial-of-service.

### Patches
The function has been refined to reject such strings without the associated resource consumption in version 3.7.

### Workarounds
Domain names cannot exceed 253 characters in length, if this length limit is enforced prior to passing the domain to the `idna.encode()` function it should no longer consume significant resources. This is triggered by arbitrarily large inputs that would not occur in normal usage, but may be passed to the library assuming there is no preliminary input validation by the higher-level application.

### References
* https://huntr.com/bounties/93d78d07-d791-4b39-a845-cbfabc44aadb

## Affected packages

- `idna < 3.7`

## Remediation

Upgrade to a patched release:

- `idna 3.7`