WebSocket Crash in Granian HTTP Server for Python Applications
CVE-2026-42544

7.5HIGH

Key Information:

Vendor

Emmett-framework

Status
Granian
Vendor
CVE Published:
12 May 2026

What is CVE-2026-42544?

Granian, a Rust-based HTTP server designed for Python applications, exhibits a vulnerability where it crashes when an unauthenticated client sends a WebSocket upgrade request containing non-ASCII bytes in the Sec-WebSocket-Protocol header. This crash occurs during the WebSocket scope construction, prior to invoking the ASGI application, resulting in disruption of service for legitimate users. This issue was present in Granian versions from 1.2.0 through 2.7.4 and has been addressed in version 2.7.4.

Affected Version(s)

granian >= 1.2.0, < 2.7.4

References

https://github.com/emmett-framework/granian/security/advi...
x_refsource_CONFIRM

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.