Emby Server SSRF is a remote code execution vulnerability affecting Emby Server, a popular self-hosted media streaming application.
The vulnerability, tracked as CVE-2020-26948, allows attackers to execute arbitrary code on the server by manipulating a URL that is processed by the server.
This vulnerability exists because Emby Server does not properly validate user-supplied input before processing it which allows attackers to inject a specially crafted URL that will be executed by the server.
This could allow attackers to steal sensitive information, install malware, or take complete control of the server.
The Emby Server SSRF vulnerability was first disclosed in December 2020. Emby released a patch for vulnerability in January 2021. However, it is important to note that many Emby servers are still vulnerable to this attack.
Here is the step-by-step explanation of this vulnerability being exploited:
- Identifying a vulnerable field
The first step is to identify a field in the Emby Server web interface that is vulnerable to SSRF. One such field is the “ImageURL” parameter in the “Items/RemoteSearch/Image” API endpoint.
This parameter allows users to specify a URL to an image that they want to add to their Emby library. However, it does not properly validate the URL, which allows attackers to inject malicious code.
- Crafting a malicious URL:
Once the attacker has identified a vulnerable field, they can craft a malicious URL that will be executed by the server. This URL can be used to do a variety of things, such as:
Steal sensitive information from the server, such as user credentials or financial data.
Install malware on the server, which can be used to launch further attacks or steal data.
Take complete control of the server and use it for malicious purposes, such as launching denial-of-service attacks or spamming other servers.
- Injecting the malicious URL
The next step is to inject the malicious URL into the vulnerable field. This can be done by tricking a user into clicking on a link that contains the malicious URL, or by using a web browser extension or plugin to inject the URL directly into the web page.
- Executing the malicious code
Once the malicious URL has been injected, the Emby Server will attempt to fetch the image from the specified URL. This will cause the server to execute the code that is contained in the URL.
What are the impacts of Emby server SSRF vulnerability
The Emby Server SSRF vulnerability (CVE-2020-26948) can have several potential impacts, including:
1. Data theft
Attackers could steal sensitive information stored on the Emby server, such as user credentials, financial data, or personal media files.
This information could then be used for identity theft, financial fraud, or blackmail.
2. Malware installation
Attackers could inject malicious code onto the Emby server, which could be used to install malware or other harmful software. This malware could then be used to steal data, launch further attacks, or disrupt the server’s operation.
3. Server takeover
In some cases, attackers could exploit the SSRF vulnerability to gain complete control of the Emby server.
This would allow them to do anything they wanted with the server, such as stealing data, deleting files, or launching attacks against other systems.
4. Denial-of-Service
Attackers could use the SSRF vulnerability to launch denial-of-service (DoS) attacks against the Emby server.
These attacks would flood the server with requests, causing it to become overloaded and unavailable to legitimate users.
5. Reputational damage
A successful attack against an Emby server could damage the reputation of the server owner or administrator. This could lead to lost business, decreased customer trust, and other negative consequences.
6. Loss of user data
If attackers steal user data from the Emby server, this could lead to a loss of trust in the Emby platform and a decrease in users.
7. Loss of financial data
If attackers steal financial data from the Emby server, this could lead to financial losses for the server owner or administrator.
8. Disruption of service
If attackers launch DoS attacks against the Emby server, this could disrupt the service and make it unavailable to legitimate users.
9. Legal liability
If attackers use the Emby server to launch attacks against other systems, the server owner or administrator could be held legally liable for the damage caused.
It is important to note that the severity of the impacts of the Emby Server SSRF vulnerability will vary depending on the specific circumstances of each case.
However, it is clear that this vulnerability can have serious consequences for individuals, businesses, and organizations that use Emby Server
How can you prevent the Emby serve SSRF vulnerabilities
Here are several ways to prevent the Emby Server SSRF vulnerability:
1. Update Emby server
The most important step is to update Emby Server to the latest version. The vulnerability was patched in version 4.1.0, so updating to this version or later will ensure that your server is protected.
2. Use a Web Application Firewall (WAF)
A WAF can help to block malicious traffic that is trying to exploit the SSRF vulnerability. There are many different WAFs available, both commercial and open source.
3. Restrict access to the Emby server web interface
By default, the Emby Server web interface is accessible to anyone on the internet. This makes it easier for attackers to exploit the SSRF vulnerability. You can mitigate this risk by restricting access to the web interface to authorized users only. This can be done by using a firewall or by configuring Emby Server to require authentication.
4. Be careful about clicking on links
Attackers often try to exploit the SSRF vulnerability by tricking users into clicking on malicious links. These links may appear in emails, on websites, or in social media posts. Be careful about clicking on links from unknown sources, and only click on links that you trust.
5. Use a web browser extension or plugin
There are several web browser extensions and plugins available that can help to protect you from SSRF vulnerabilities. These extensions and plugins can block malicious traffic, or they can warn you about potential risks before you click on a link.
By following these steps, you can help to protect your Emby Server from the SSRF vulnerability and other security threats.
