Hi

Thanks for the report and the patch.

We could also catch this exception in the big try-except clause in __call__, and we could catch the more generic UnicodeError. But that would perhaps catch too much - also things that really are programming errors and shouldn't give a 400 reply.

I think I would prefer to just catch this Unicode error if it happens, rather than trying to trigger it early. Perhaps by wrapping the call of _basic_security_checks. Do  you think that would catch too much or too little?

/Mads



On 26/08/2024 17:06, Valentin Kleibel wrote:
Hi,

we have recently noticed a lot of errors in Kallithea from probing for a php vulnerability [1] looking like: "WebApp Error: UnicodeDecodeError: 'utf-8' codec can't decode byte 0xad in position 0: invalid start byte"

This can be reproduced with curl:
curl https://example.com/?%AD

The error stems from webob naively trying to utf-8 decode all %-encoded bytes in URL-parameters.

In my opinion this exception should be handled and a error 400 should be returned.

Attached you can find a small patch i created to check for this in kallithea/controllers/base.py:_basic_security_checks().

Best Regards,
Valentin


[1] https://devco.re/blog/2024/06/06/security-alert-cve-2024-4577-php-cgi-argument-injection-vulnerability-en/

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