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Golam_Mostafa

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SSRF Attacks: The Silent Threat Hiding in Your Server

What is SSRF (Server-Side Request Forgery)?

Server-Side Request Forgery (SSRF) is a web vulnerability where attackers trick a server into making unauthorized requests to internal or external systems.

How Does It Work?

An attacker sends a malicious URL in a request that the server processes as legitimate. The server then makes the request on the attacker’s behalf.

Example:

A shopping app checks stock by making a backend API request:

POST /product/stock  
stockApi=http://stock.server.com/check?productId=6&storeId=1  
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An attacker modifies the URL to point to the server's admin page:

POST /product/stock  
stockApi=http://localhost/admin  
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The server fetches and returns restricted admin data, bypassing access controls.

Why Does This Happen?

  1. Access Control Gaps: Checks are skipped for local requests.
  2. Recovery Features: Admin access is granted to local users without authentication.
  3. Hidden Interfaces: Admin tools on separate ports trust local machine requests.

Protect Against SSRF

  • Validate and sanitize input URLs.
  • Use URL whitelists.
  • Restrict internal service access.

SSRF can be critical, but good design and input validation can prevent it.


Acknowledgment: This document references information from PortSwigger Web Security and ChatGPT.


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