An XML External Entity attack (XXE attack) is a type of attack against an XML input parsing program. This attack occurs when an XML parser that is weakly designed processes XML information containing an external object relation. In this article, we will discuss XEE attack, XML external entity, XEE example, XEE prevention and, XEE vulnerability.
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XXE is a vulnerability of web security that allows an application to interfere with XML data processing by an attacker. Often, it helps an attacker to view files on the filesystem of the application server and to communicate with any backend or external structures accessed by the application itself. This attack can lead to sensitive data disclosure, denial of service, forgery of server-side requests, port scanning from the perspective of the computer where the parser is located, and other impacts on the device.
The simple answer to this question, XEE vulnerability can be triggered when
Is that the XEE (XML Eternal Entity Injection) vulnerability can be activated when certain endpoints that accept XML as input are detected. But often, you may find cases where the endpoints that accept XML may not be so evident (for example, those cases where the client uses only JSON to access the service). In these situations, a pen tester must try various things to see how the application reacts, such as changing the HTTP methods, Content-Type, etc. If the content is parsed by the application, then there is a scope for XXE.
Various forms of XXE attacks exist:
There are two ways:
The attack surface of XXE vulnerabilities is less apparent in certain unusual instances.
There are two options you have – manual or automatic. The overwhelming majority of XXE Vulnerabilities can be identified for you easily and accurately by Burp Suite Specialist.
Checking for XXE vulnerabilities manually normally involves:
Virtually all XXE vulnerabilities occur because the XML parsing library of the application supports potentially hazardous XML features not necessary or expected to be used by the application. Disabling such features is the simplest and most effective way of avoiding XXE attacks.
Generally, disabling the resolution of external entities and disabling support for XInclude is appropriate. This can usually be done through configuration options or by overriding the default behaviour programmatically.
The addition of XXE attacks to the OWASP top 10 in 2017 as a new category was the result of an increased attack presence in many environments of this type of vulnerability. XXE was used by attackers to manipulate poorly configured XML processors, which are set by default in many instances, to allow an external entity relation to be defined within XML documents. By uploading XML documents or by manipulating insecure code and third-party dependencies, attackers have discovered ways to expose this vulnerability by using external entities for attacks.
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