CVE-2026-63374
AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
CVSS Score
0.0
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-295 CWE-297 |
| Vendor | agronholm |
| Product | anyio |
| Published | Sep 22, 2026 |
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Affected Versions
agronholm / anyio
< 4.14.2
References
github.com: https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6 github.com: https://github.com/agronholm/anyio/pull/1208 github.com: https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce github.com: https://github.com/agronholm/anyio/releases/tag/4.14.2