CVE-2026-63374

Name	CVE-2026-63374
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1148561

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
python-anyio (PTS)	bookworm	3.6.2-1	vulnerable
	trixie	4.8.0-3	vulnerable
	forky, sid	4.15.1-3	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
python-anyio	source	(unstable)	4.15.1-1			1148561

Notes

https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6
https://github.com/agronholm/anyio/pull/1208
Fixed by: https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce (4.14.2)