CVE-2026-42544: Granian: Unauthenticated DoS via WebSocket subprotocol header panic

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-10-26
Weakness: CWE-20

Description

Granian is a Rust HTTP server for Python applications. From 1.2.0 to 2.7.4, 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 vulnerability is fixed in 2.7.4.

Affected products

emmett-framework granian: from 1.2.0, < 2.7.4

References

https://github.com/emmett-framework/granian/security/advisories/GHSA-vrg7-482j-p6f6
https://github.com/emmett-framework/granian/security/advisories/GHSA-vrg7-482j-p6f6

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