Friday, July 21, 2023

Re: GWT RPC call recognized as a Java Method Injection by Fortiweb

On Friday, July 21, 2023 at 11:38:59 AM UTC+2 wrote:
We have one deployment of a GWT app where there is a Fortiweb firewall that blocks every GWT RPC call because it recognizes every call as a Java Method Injection attack. This seems to be caused by the presence of the pattern "java.lang." in the messages from the client to the server like the following:

My idea is to convince the firewall administrator that these are false-positives as these calls are part of the GWT RPC mechanism that does not allow arbitrary java code execution on the server side.

Is my reasoning correct or am I not worried enough?

Your reasoning is correct. But you can also obfuscate type names to prevent triggering the WAF: 
(disclaimer: I haven't used RPC for more than 10 years)

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