server side code execution vulnerbility

trojan81
trojan81 used Ask the Experts™
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Experts,

This question relates to cyber security and service side code execution.

In many cases I read about a vulnerability that allows an attacker to upload files.  However, how do they get the file to execute?  Normally it is mentioned as "vulnerability allowed for attacker to upload and execute the malicious payload".  I would see uploading and being able to tell the server to execute it as two separate functions that require two separate exploits.  Thoughts?
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Fractional CTO
Distinguished Expert 2018
Commented:
Correct. Upload + Execute are two separate actions.

Whether you count this as one or two exploits, result is the same. If code can be uploaded + run, then exploit's can occur.

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Commented:
DAvid,

It's the code that is instructing the server to download and RUN the file.  What's an example or how might that code look?
btanExec Consultant
Distinguished Expert 2018
Commented:
It is a two operation though related.

If the input from the XML data is not properly validated, it could leave you vulnerable to many attack possibilities, such as Server Side Request Forgery, Local File Read, Denial of Service, and XML External Entity (XXE) injection attack.  The article run through example and mainly is the server parsing the document did not handle well hence allowing code to be executed.

https://www.google.com/amp/s/www.we45.com/blog/3-ways-an-xxe-vulnerability-could-hit-you-hard%3fhs_amp=true

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