XXE Injection Attacks – XML External Entity Vulnerability With Examples


XXE Injection Attacks or XML External Entity vulnerabilities are a specific type of Server Side Request Forgery or SSRF attack relating to abusing features within XML parsers.

XXE Injection Attacks - XML External Entity Vulnerability With Examples

The features these attacks go after are widely available but rarely used and when trigged can cause a DoS (Denial of Service) attack and in some cases much more serious escalation like extraction of sensitive data or in worst case scenarios RCE or Remote Code Execution.

What is XML

In computing, Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.

From: https://en.wikipedia.org/wiki/XML

It’s been replaced in a lot of modern APIs by JSON, but a lot of applications still use XML and/or have XML parsers inside so it’s good to be aware of XXE attacks as a vector.

XML parsers validate data in two main ways, XXE falls within the DTD or Data Type Definition method.

What is an XXE Attack

The thing is the XML entities can be defined anywhere, including externally, this is where XXE comes in and can be abused by an attacker by using XML entities to request the execution of certain files or even to return the contents of files if they know the structure of your web application for example.

It’s also worth mentioning, that with some XML parsers, it’s even possible to get directory listings in addition to the contents of a file.

XXE Attack Example

An example would look like this:

Request

Response

Obviously this is a simple example, but it could be used to echo /etc/passwd, get secrets from source code repos or execute malicious code (like a web shell) if the attacker has managed to upload something.

You can find out more, in much more depth, here:

Part 1 – What is XML External Entity (XXE)?
Part 2 – XML External Entity (XXE) limitations
Part 3 – Out-of-band XML External Entity (OOB-XXE)

Posted in: Exploits/Vulnerabilities

,


Latest Posts:


HiddenWall - Create Hidden Kernel Modules HiddenWall – Create Hidden Kernel Modules
HiddenWall is a Linux kernel module generator used to create hidden kernel modules to protect your server from attackers.
Anteater - CI/CD Security Gate Check Framework Anteater – CI/CD Security Gate Check Framework
Anteater is a CI/CD Security Gate Check Framework to prevent the unwanted merging of filenames, binaries, deprecated functions, staging variables and more.
Stardox - Github Stargazers Information Gathering Tool Stardox – Github Stargazers Information Gathering Tool
Stardox is a Python-based GitHub stargazers information gathering tool, it scrapes Github for information and displays them in a list tree view.
ZigDiggity - ZigBee Hacking Toolkit ZigDiggity – ZigBee Hacking Toolkit
ZigDiggity a ZigBee Hacking Toolkit is a Python-based IoT (Internet of Things) penetration testing framework targeting the ZigBee smart home protocol.
RandIP - Network Mapper To Find Servers RandIP – Network Mapper To Find Servers
RandIP is a nim-based network mapper application that generates random IP addresses and uses sockets to test whether the connection is valid or not with additional tests for Telnet and SSH.
Nipe - Make Tor Default Gateway For Network Nipe – Make Tor Default Gateway For Network
Nipe is a Perl script to make Tor default gateway for network, this script enables you to directly route all your traffic from your computer to the Tor network.


Comments are closed.