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EUVD-2026-319280

fkie_cve-2026-42544

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.

GHSA-vrg7-482j-p6f6 — Granian vulnerable to unauthenticated DoS via WebSocket subprotocol header panic

Affected: PyPI: granian

### 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

https://github.com/emmett-framework/granian/blob/bdd5b0fbbb2aca6f2f4c0d2700c244d190958035/src/asgi/utils.rs#L122-L125

`HeaderValue::to_str()` returns `Err` for bytes outside visible ASCII. The subsequent `.unwrap()` panics.

In release builds Granian sets `panic = "abort"`, so this panic terminates the worker instead of being handled as a normal request error.

### PoC

#### Step 1. starts a Granian ASGI server

```python # app.py async def app(scope, receive, send): if scope["type"] == "websocket": await receive() await send({"type": "websocket.accept"}) return

await send({"type": "http.response.start", "status": 200, "headers": []}) await send({"type": "http.response.body", "body": b"ok"}) ```

```bash granian --interface asgi app:app --host 127.0.0.1 --port 8000 ```

#### Step 2. sending a raw upgrade request with `Sec-WebSocket-Protocol: \x80\xff` reached this code path and caused the worker to abort.

```python # ws-subproto-crash.py import base64, os, socket, sys

host, port, path = sys.argv[1], int(sys.argv[2]), sy…

PYSEC-2026-2503 — Granian vulnerable to unauthenticated DoS via WebSocket subprotocol header panic