CVE-2026-63374AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.3 CRITICAL (v4.0, CNA)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
- Weakness (CWE)
- CWE-295, CWE-297
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- Sep 28, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
agronholm anyio agronholm:anyio (from the name) | before 4.14.2 | CNA record |
References
- https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6x-refsource-confirm
- https://github.com/agronholm/anyio/pull/1208x-refsource-misc
- https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2cex-refsource-misc
- https://github.com/agronholm/anyio/releases/tag/4.14.2x-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.