Granian vulnerable to unauthenticated DoS via WebSocket subprotocol header panic — CVE-2026-42544

Summary

### Summary Granian aborts a worker process when an unauthenticated client sends a WebSocket upgrade request whose `Sec-WebSocket-Protocol` header contains non-ASCII bytes. The crash happens in Granian's WebSocket scope construction path, before the ASGI application is invoked. This is a single-request Denial Of Service against one worker. Repeating the request across workers takes the service offline. ### Details…

Product

pip: granian

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

Related advisories