“SSRF to RCE” A case study in exploiting chained vulnerabilities
Server-Side Request Forgery (SSRF) vulnerabilities are known to be serious, allowing attackers to manipulate requests from a web application. In this article, we’ll dive into a real-world case study that showcases the transformation of an SSRF vulnerability into a Remote Code Execution (RCE) attack by chaining multiple vulnerabilities together. This example underscores the importance of robust security measures and the need for comprehensive testing and vigilance in the world of web security.
The SSRF Vulnerability
Our story begins with the discovery of an SSRF vulnerability in a web application. The vulnerability allowed an attacker to manipulate the application’s requests to access internal resources and external services. The attacker could make HTTP requests to any reachable destination, including resources residing within the corporate network.
The Initial SSRF Exploitation
The attacker initially exploited the SSRF vulnerability to gain access to the web application’s internal services. They used this access to traverse the internal network and gather information about the infrastructure. Through careful probing, the attacker discovered a misconfigured internal API that was vulnerable to XML External Entity (XXE) injection.
XXE Injection Exploitation
The attacker crafted malicious XML payloads that exploited the XXE vulnerability, leading to the retrieval of sensitive configuration files from the internal network. These files contained crucial data, including database credentials and encryption keys.
Leveraging the Retrieved Data
With access to the database credentials and encryption keys, the attacker could now manipulate the database directly. They inserted a backdoor into the database, granting them control over application data and increasing their privileges.
Escalating to Remote Code Execution (RCE)
The attacker went further by exploiting an RCE vulnerability in the application’s outdated component. They uploaded a malicious script that allowed them to execute arbitrary code on the application server. This gave them full control over the application, with the potential to compromise the entire server.
Mitigation and Prevention
- Patch Management → Regularly update and patch all components, libraries, and dependencies in your application to mitigate known vulnerabilities.
2. Input Validation → Implement strict input validation and sanitization practices to prevent SSRF attacks.
3. Least Privilege → Apply the principle of least privilege to restrict the permissions of application components, limiting their access to internal resources.
4. Web Application Firewalls (WAFs) → Use a WAF to detect and block suspicious requests, including SSRF attempts.
5. Access Control → Restrict access to internal resources and sensitive data based on the principle of need-to-know.
6. Security Testing → Perform thorough security testing, including penetration testing and code reviews, to identify and remediate vulnerabilities in your application.
The case study of an SSRF vulnerability evolving into an RCE attack is a stark reminder of the critical importance of security in the digital age. Web applications and cloud services can be complex, and vulnerabilities often hide in plain sight. By staying informed about evolving threats, continuously monitoring for vulnerabilities, and implementing robust security measures, organizations can reduce the risk of falling victim to chained attacks like the one described in this article. Security should be proactive and vigilant, not just a reactive afterthought.
