{"id":"GHSA-82r6-8w77-94w6","summary":"AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing","details":"### Impact\nServices 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.\n\n### Patches\nThe vulnerability will be patched in v4.14.2.\n\n### Workarounds\nEncode host names via the `idna` package prior to connecting.","aliases":["CVE-2026-63374","PYSEC-2026-4025"],"modified":"2026-10-01T17:55:34.261886042Z","published":"2026-09-18T17:17:18Z","database_specific":{"nvd_published_at":null,"cwe_ids":["CWE-295","CWE-297"],"severity":"CRITICAL","github_reviewed":true,"github_reviewed_at":"2026-09-18T17:17:18Z"},"references":[{"type":"WEB","url":"https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6"},{"type":"WEB","url":"https://github.com/agronholm/anyio/pull/1208"},{"type":"WEB","url":"https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce"},{"type":"PACKAGE","url":"https://github.com/agronholm/anyio"},{"type":"WEB","url":"https://github.com/agronholm/anyio/releases/tag/4.14.2"}],"affected":[{"package":{"name":"anyio","ecosystem":"PyPI","purl":"pkg:pypi/anyio"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.14.2"}]}],"versions":["1.0.0","1.0.0a1","1.0.0a2","1.0.0b1","1.0.0b2","1.0.0rc1","1.0.0rc2","1.1.0","1.2.0","1.2.1","1.2.2","1.2.3","1.3.0","1.3.1","1.4.0","2.0.0","2.0.0b1","2.0.0b2","2.0.0rc1","2.0.0rc2","2.0.1","2.0.2","2.1.0","2.2.0","3.0.0","3.0.0rc1","3.0.0rc2","3.0.0rc3","3.0.0rc4","3.0.1","3.1.0","3.2.0","3.2.1","3.3.0","3.3.1","3.3.2","3.3.3","3.3.4","3.4.0","3.5.0","3.6.0","3.6.1","3.6.2","3.7.0","3.7.0rc1","3.7.1","4.0.0","4.0.0rc1","4.1.0","4.10.0","4.11.0","4.12.0","4.12.1","4.13.0","4.14.0","4.14.1","4.2.0","4.3.0","4.4.0","4.5.0","4.5.1","4.5.2","4.6.0","4.6.1","4.6.2","4.6.2.post1","4.7.0","4.8.0","4.9.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-82r6-8w77-94w6/GHSA-82r6-8w77-94w6.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}