---
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: '2026-09-28'
sourceUpdated: '2026-09-28T17:17:50.357'
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'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63374.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-63374'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2538958'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63374'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63374'
  - url: 'https://access.redhat.com/errata/RHSA-2026:73929'
  - url: 'https://access.redhat.com/errata/RHSA-2026:73930'
  - url: 'https://pypi.org/project/anyio'
  - url: 'https://access.redhat.com/errata/RHSA-2026:79378'
  - url: 'https://access.redhat.com/errata/RHSA-2026:84734'
tags:
  - nvd
  - cve.org
  - osv
  - pip
  - ghsa
  - csaf
  - vex
  - red-hat
aliases:
  - GHSA-82r6-8w77-94w6
  - PYSEC-2026-4025
ecosystem: pip
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-09-28T16:07:36.655203Z'
cvssSource: cna
ingestedAt: '2026-09-18T17:46:41.530Z'
epss: 0.00289
epssPercentile: 0.21585
scores:
  cna: 9.3
  vendor: 7.4
---

## 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

## Vendor advisories

- **RHSA-2026:73929** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-09-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:73929)
- **RHSA-2026:73930** · Red Hat · fixed in: Red Hat AI Inference Server 3.2 · released 2026-09-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:73930)
- **Red Hat VEX** · Moderate · affected: Confidential Compute Attestation, Exploit Intelligence, Lightspeed Core, Migration Toolkit for Applications 8, Migration Toolkit for Containers, OpenShift Lightspeed, … · no fix planned: Red Hat Ansible Automation Platform 2, Red Hat AI Inference Server, Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat OpenShift AI (RHOAI), … · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63374.json)
- **RHSA-2026:79378** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.7 · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:79378)
- **RHSA-2026:84734** · Red Hat · fixed in: Red Hat OpenShift AI 3.4 · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84734)