Description
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.
Published: 2026-09-22
Score: 9.3 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

No vendor fix or workaround currently provided.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

Sign in to view the affected projects.

Advisories
Source ID Title
Github GHSA Github GHSA GHSA-82r6-8w77-94w6 AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
History

Tue, 22 Sep 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Agronholm
Agronholm anyio
Vendors & Products Agronholm
Agronholm anyio

Tue, 22 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
Description 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.
Title AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
Weaknesses CWE-295
CWE-297
References
Metrics cvssV4_0

{'score': 9.3, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-22T15:23:14.259Z

Reserved: 2026-07-16T17:39:30.170Z

Link: CVE-2026-63374

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-22T16:17:50.680

Modified: 2026-09-22T16:17:50.680

Link: CVE-2026-63374

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-22T17:45:17Z

Weaknesses