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XML External Entities (XXE)

What is XML External Entities (XXE) injection?​

XML External Entities (XXE) injection is a type of security vulnerability that allows attackers to exploit the processing of XML data by an application.

This occurs when an application accepts XML data from an untrusted source and processes it without proper validation, allowing the inclusion of external entities that can be malicious or contain sensitive information.

As a result, attackers can perform various malicious activities, such as stealing user data, executing arbitrary code, or performing denial-of-service attacks.

Check out this video for a high-level explanation:

What is the impact of XXE injection?​

XML External Entities (XXE) injection can lead to various security threats and risks, such as:

  • Information theft: XXE attacks can steal sensitive information, such as login credentials, credit card details, or other personally identifiable information, by injecting malicious code or entities that collect and transmit user data to attackers.
  • Server-side request forgery: XXE attacks can initiate requests to systems that are accessible from the affected web server.
  • Denial of service: XXE attacks can cause denial-of-service (DoS) attacks by injecting malicious code or entities that consume system resources, such as CPU or memory, leading to system crashes or slowdowns.
  • Arbitrary code execution: XXE attacks can execute arbitrary code on the server by injecting malicious code or entities that exploit vulnerabilities in the application or the underlying operating system.

How to prevent XXE injection?​

To prevent XML External Entities (XXE) injection, it is important to follow security best practices and implement appropriate security measures, such as:

  • Disable external entity processing: Disable the processing of external entities in XML parsers and libraries to prevent XXE vulnerabilities.
  • Use secure parsers and libraries: Use secure parsers and libraries that support secure XML processing.
  • Use input validation: Validate user input to ensure that it is safe and does not contain malicious code or entities.
  • Keep software up to date: Keep software and security protocols up to date, as new vulnerabilities and security patches are regularly released.

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Explanation & Prevention​

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Last updated on by Stefan Streichsbier