ProxyHeadersMiddleware crashes with gunicorn 24.1.0: AttributeError 'str' object has no attribute '_version'

[user-Roma]

Summary

_TrustedHosts in proxy_headers.py crashes when used with gunicorn 24.1.0 due to type mismatch in trusted hosts handling.

Versions

• uvicorn: 0.40.0
• gunicorn: 24.1.0 (works fine with 24.0.0)
• uvicorn-worker: 0.4.0
• Python: 3.13

Error

File "/opt/pysetup/venv/lib/python3.13/site-packages/uvicorn/middleware/proxy_headers.py", line 95, in __init__
    if "/" in host:
       ^^^^^^^^^^^
File "/usr/local/lib/python3.13/ipaddress.py", line 741, in __contains__
    if self._version != other._version:
                        ^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute '_version'

Root Cause

Gunicorn 24.1.0 added CIDR network support (PR #3449) and now passes pre-parsed ipaddress.IPv4Network objects to uvicorn worker instead of raw strings.

In _TrustedHosts.__init__, the code attempts if "/" in host to detect CIDR notation, but host is already an IPv4Network object. The in operator triggers IPv4Network.__contains__(), which expects an IP address object, not a string "/".

Expected Behavior

Uvicorn should handle both string and pre-parsed ipaddress objects from gunicorn.

Workaround

Pin gunicorn to version < 24.1.0:

pip install gunicorn==24.0.0

[Kludex]

They solved it.