CVE-2026-63374

critical · 9.3

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.

9.3

CVSS

0.3%

EPSS (exploit prob.)

24th

EPSS percentile

2026-09-22

Published

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Weaknesses

CWE-295CWE-297

References

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

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2026-63374