---
id: CVE-2026-63374
title: >-
  AnyIO is a high level asynchronous concurrency and networking framework that
  works on top of either Trio or asyncio
summary: >-
  AnyIO is a high level asynchronous concurrency and networking framework that
  works on top of either Trio or asyncio. Prior to 4.14.2, connect_tcp() and
  TLSStream.wrap() can validate internationalized host names after the standard
  library…
severity: critical
cvss: 9.3
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'
cwe:
  - CWE-295
  - CWE-297
vendor: agronholm
product: anyio
affected:
  - anyio < 4.14.2
patched:
  - anyio 4.14.2
published: '2026-09-22'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T21:16:28.120'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63374'
references:
  - url: >-
      https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce
    label: security-advisories@github.com
  - url: 'https://github.com/agronholm/anyio/pull/1208'
    label: security-advisories@github.com
  - url: 'https://github.com/agronholm/anyio/releases/tag/4.14.2'
    label: security-advisories@github.com
  - url: 'https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6'
    label: security-advisories@github.com
  - url: 'https://github.com/agronholm/anyio'
  - url: 'https://github.com/advisories/GHSA-82r6-8w77-94w6'
tags:
  - nvd
  - cve.org
  - osv
  - pip
  - ghsa
epss: 0.00289
epssPercentile: 0.19152
aliases:
  - GHSA-82r6-8w77-94w6
ecosystem: pip
cvssSource: cna
ingestedAt: '2026-09-18T17:46:41.530Z'
---

## Overview

AnyIO is a high level asynchronous concurrency and networking framework that works on top of either Trio or asyncio. Prior to 4.14.2, connect_tcp() and TLSStream.wrap() can validate internationalized host names after the standard library converts them with IDNA 2003 instead of IDNA 2008. When a connection to a non-ASCII domain is hijacked or redirected, an attacker can obtain a legitimate certificate for the different ASCII hostname produced by IDNA 2003 and present it to the client, causing the malicious endpoint's certificate to validate. This issue is fixed in version 4.14.2.

## Remediation

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

## Package advisory (CVE-2026-63374)

Affected packages:

- `anyio < 4.14.2`

Patched in:

- `anyio 4.14.2`

Source: https://osv.dev/vulnerability/GHSA-82r6-8w77-94w6