AnyIO: TLSStream IDNA 2003 host name encoding enables potential TLS certificate spoofing — GHSA-82R6-8W77-94W6

Summary

### 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…

Timeline

Published by source

2026-09-18

Risk context

• Reported severity or threat level: critical.
• Reported CVSS score: 9.3 out of 10.
• Review exposure for the affected product or family: pip: anyio.

Product

pip: anyio

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-82R6-8W77-94W6

Source

GitHub

Vendor

GitHub

Published by source

2026-09-18

Last source activity

2026-09-18

Additional identifiers

CVE-2026-63374

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.