AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
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.
CVE-2026-63374
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-63374
anyio
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "agronholm",
"product": "anyio",
"versions": [
{
"status": "affected",
"version": "< 4.14.2"
}
]
}
]- Related CVEs
- CVE-2026-63374
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #3205 · Revision 1
- Added to Heist Feed
- Publisher date