{"cve":"CVE-2026-63374","nvd":{"published":"2026-09-22T16:17:50.680","modified":"2026-09-28T17:17:50.357","status":"Awaiting Analysis","description":"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_v4":{"vector":"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","score":9.3},"cvss_v3":null,"cwes":["CWE-295","CWE-297"],"references":["https://github.com/agronholm/anyio/commit/68f58915f82d9be8109ebbbd8f5d70577d43f2ce","https://github.com/agronholm/anyio/pull/1208","https://github.com/agronholm/anyio/releases/tag/4.14.2","https://github.com/agronholm/anyio/security/advisories/GHSA-82r6-8w77-94w6"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:56:02.509636177+00:00"},"epss":{"cve":"CVE-2026-63374","score":0.00289,"percentile":0.21496,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-82r6-8w77-94w6","url":"https://osv.dev/vulnerability/GHSA-82r6-8w77-94w6","summary":"AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing","modified":"2026-10-01T17:56:11.058322399Z","packages":[{"ecosystem":"PyPI","name":"anyio","purl":"pkg:pypi/anyio","ranges":["<4.14.2"],"fixed":["4.14.2"]}]},{"id":"PYSEC-2026-4025","url":"https://osv.dev/vulnerability/PYSEC-2026-4025","summary":"AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing","modified":"2026-10-01T17:45:01.997111942Z","packages":[{"ecosystem":"PyPI","name":"anyio","purl":"pkg:pypi/anyio","ranges":["<4.14.2"],"fixed":["4.14.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}