Aiohttp.server 'Invalid char in url path' errors

I am getting tons of these errors:

Logger: aiohttp.server
Source: /usr/local/lib/python3.10/site-packages/aiohttp/web_protocol.py:403
First occurred: 31. mája 2023 o 13:26:04 (51818 occurrences)
Last logged: 12:23:16

Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_protocol.py", line 332, in data_received
    messages, upgraded, tail = self._request_parser.feed_data(data)
  File "aiohttp/_http_parser.pyx", line 551, in aiohttp._http_parser.HttpParser.feed_data
aiohttp.http_exceptions.InvalidURLError: 400, message='Invalid char in url path'

I am unable to debug where is it coming from. I have set aiohttp.server to debug log level, but it didn’t reveal any more information than this. Is there any way how to at least log the actual URL that caused the issue? That might give some hints as to where the problem lies.
There are no apparent problems with Home Assistant so I don’t know where to start.

Are you HA server reachable from outside through a portforward?
If so, then you are probably being hit by scripts testing your system for known vulnarabilities and for logging of your system setup and services for maybe later attacks.

It is reachable, not through a portforward, but through a reverse proxy with a specific virtualhost, which is not likely to be guessed by anyone, however I have completely disabled the reverse proxy just to be sure and the errors still kept appearing, so this is not the case…

If it was me with this case, then I would install wiresharkand listen to what comes over the network, but it might require a bit of technical knowledge

Wireshark is freeware, so it cost nothing to try though.

Well, I will probably have to do it.
Is it possible to install wireshark directly on HA?

No
You will have to install it on another machine and if the error is in an addon or integration, then you might not see it in wireshark, because it just runs on the virtual network.
If the case is an addon or integration, then addons’ can be stopped and I think integrations can be disabled.