GHSA-82r6-8w77-94w6
AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing
At a glance
- Published
- Updated
- CVE
- CVE-2026-63374
- Aliases
- PYSEC-2026-4025
- CVSS_V4
- 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
Description
### Impact Services using internationalized (non-ASCII) domain names are potentially vulnerable to TLS connections made from AnyIO's `connect_tcp()` or directly via `TLSStream.wrap()` where the connection has (through other means) been hijacked and redirected to a malicious server. The attacker would obtain a legitimate certificate using the IDNA 2003 encoded version of the domain name and offer it to the connecting client, making the certificate validate properly on the client's end. ### Patches The vulnerability will be patched in v4.14.2. ### Workarounds Encode host names via the `idna` package prior to connecting.
Affected packages
| Package | Versions |
|---|---|
| PyPI · anyio | introduced 0, fixed 4.14.2 |
References
- https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6 WEB
- https://github.com/agronholm/anyio/pull/1208 WEB
- https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce WEB
- https://github.com/agronholm/anyio PACKAGE
- https://github.com/agronholm/anyio/releases/tag/4.14.2 WEB
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — GitHub Advisory Database |