CVE-2026-42545 — Granian: DoS via WSGI response header panic

Affected: emmett-framework granian

Granian is a Rust HTTP server for Python applications. From 0.2.0 to 2.7.4, Granian aborts a worker process if a WSGI application returns an invalid HTTP response header name or value. The WSGI response conversion path uses .unwrap() on both the header name and header value constructors, so malformed output from the application becomes a process abort instead of a handled error. This vulnerability is fixed in 2.7.4.

GHSA-f5p7-9fr5-8jmj — Granian vulnerable to DoS via WSGI response header panic

Affected: PyPI: granian

### Summary

Granian aborts a worker process if a WSGI application returns an invalid HTTP response header name or value. The WSGI response conversion path uses `.unwrap()` on both the header name and header value constructors, so malformed output from the application becomes a process abort instead of a handled error.

This issue requires a buggy or attacker-influenced WSGI application to emit invalid headers. It is not a parser bug in Granian's request path. The security impact is that application mistakes which should result in a `500` instead kill the worker process.

### Details

https://github.com/emmett-framework/granian/blob/bdd5b0fbbb2aca6f2f4c0d2700c244d190958035/src/wsgi/io.rs#L39-L42

If either conversion fails, `.unwrap()` panics. In release builds Granian uses `panic = "abort"`, so the panic terminates the worker.

#### Preconditions

The attacker must be able to influence a header name or value produced by the WSGI application, or the application must otherwise generate invalid headers.

Examples include:

- a header name containing a space - a header value containing `\r\n` - a header value containing a null byte

These are realistic failure modes for applications that reflect user-controlled data into headers such as `Location`, `Content Disposition`, or custom response headers.

### PoC

#### Step 1

start Granian with the PoC WSGI app

```python # app.py def app(environ, start_response): path = environ.get("PATH_INFO", "/") if path == "/crash-name…

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CVE-2026-42545 — Granian: DoS via WSGI response header panic

GHSA-f5p7-9fr5-8jmj — Granian vulnerable to DoS via WSGI response header panic