Definition of Server Side Request Forgery (SSRF). Know Its Types, Impact, and Prevention Practices

Introduction

In the past few years, the risk of cyberattacks has grown enormously. In fact, more than 800,000 people experience data security breaches every year, which is quite concerning.

Looking at these numbers, the safekeeping of web applications has become vital.

Now, one significant threat to any web application is server-side request forgery or SSRF. This cyberattack helps the hacker trick the server to reveal sensitive information or access internal systems.

By the end of this blog, you will have a clear understanding of SSRF and how you can equip yourself to defend your web applications from attackers. Let’s begin and learn how to keep your system safe and secure.

Meaning of SSRF

Server-side request forgery, or SSRF, is a cyber-attack where the attacker exploits vulnerabilities in a web application to manipulate server-side requests. These attacks primarily target applications that import or allow data retrieval from URLs.

Let’s break it down in simpler terms.

Imagine you’re using a web app that can fetch information from other websites. You simply enter a URL, and the app gets the data for you. Sounds straightforward, right? But there’s a risk here.

A hacker can enter a malicious URL instead of a trusted one. Not being cautious, the app fetches data from this harmful URL and allows attackers to expose sensitive information or perform unwanted actions.

SSRF is a very dangerous cyberattack because it exploits a server’s trust within its network system. However, most organizations think traffic within their internal network is very secure and do not need strict security measures for internal communications.

However, the fact is that attackers exploit this vulnerability and trick the server into making requests that cause severe problems, such as data breaches and unauthorized access.

The SSRF technique can also target external systems. The attacker can use requests like scanning for open ports or interacting with APIs to attack other servers. As technology progresses, SSRF is becoming a potent technique that attackers use to serve their malicious purposes.

What Are The Impacts of SSRF Attacks ?

Now that we clearly understand SSRF, we will delve into the severe impacts these cyber attacks can bring to your organization.

Data Breaches

This is one of the most significant risks of SSRF attacks. The attacker has the capability of tricking your server into accessing any sensitive information, such as customer data or any type of intellectual property.

If this happens, then the organization may face a loss of trust from the customers or maybe some legal troubles, and they have to pay heavy fines as well.

Unauthorized Access to Internal Resources

SSRF accounts give the hacker the chance to access your internal network as well. Once the hacker gets access to the internal system, they can harm it, install malware, and steal more data.

Damage to Reputation

An SSRF attack can harm your reputation and finances as well. If your customers’ data gets leaked, they will lose faith in the company. This loss of faith will cause a drop in your sales. Also, you might face legal action and have to spend a lot of money to get rid of those legal actions.

The Types of SSRF Attacks

Let’s explore some of the common types of SSRF attacks.

SSRF Targeting the Server

In this attack, the hacker can trick the web application into sending requests to the hosting server. For example, an eCommerce site checks if a product is in stock by sending a URL request to the backend API.

But if this URL isn’t secure, the attacker can change it to point to a local URL. The server will trust this request and give the hacker unauthorized access.

Blind SSRF

In blind SSRF, the attacker can’t directly see the response from the server. In this attack, they make the server perform harmful tasks. For example, the attacker might request a large file repeatedly to cause the server to crash, resulting in a denial of service (DoS) attack.

SSRF Targeting the Back End

Here, the hacker targets internal backend systems. These are the systems a regular user can’t access and have weak security because they’re not for public use. However, the weakness gives the attacker access to sensitive internal functions, which might trick the server into interacting with internal administrative interfaces.

In our next section, we will be learning more about Blind SSRF and how you can combat it.

Vulnerabilities of Blind SSRF

Blind SSRF vulnerabilities are tricky techniques because you can’t see any response in this one. However, below are some of the best ways to find these vulnerabilities:

Use out-of-band (OAST) techniques, as these trigger an HTTP request to an external system that is in your control and allows for interactions.

Even if you find the blind SSRF vulnerability and know that the server can make requests, you still can’t see the responses. However, you can look for other vulnerabilities on the server or in the backend systems. Scan the internal IP addresses for known vulnerabilities using blind out-of-band techniques or send payloads to detect unpatched servers.

Another effective strategy for identifying blind SSRF vulnerabilities is to focus on internal scanning. You can send requests to the internal IP addresses. This way, you can identify services and applications running within the organization’s network that might be vulnerable to SSRF attacks.

Identify hidden security gaps by using automated tools that external attackers may exploit. This is a more effective way to quickly detect and respond to any vulnerability, keeping the internal network secure.

Also, if you connect the application to a system you can control, you can send malicious responses back. However, this method might exploit client-side vulnerabilities in the server’s HTTP implementation and lead to remote code execution within the application.

Curious to know more? Then Check the detailed guide about how to defend against Server-Side Request Forgery (SSRF) and mitigating SSRF effectively.