Cyberis Blog

Reassuringly clear thinking.

  • Research

Vulnerabilities That Just Won't Die - Compression Bombs

Recently Cyberis has reviewed a number of next-generation firewalls and content inspection devices - a subset of the test cases we formed related to compression bombs - specifically delivered over HTTP. The research prompted us to take another look at how modern browsers handle such content given that the vulnerability (or perhaps more accurately, ‘common weakness’ - http://cwe.mitre.org/data/definitions/409.html) has been reported and well known for over ten years. The results surprised us - in short, the majority of web browsers are still vulnerable to compression bombs leading to various denial-of-service conditions, including in some cases, full exhaustion of all available disk space with no user input.

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  • Tools and techniques

Egresser - Tool To Enumerate Outbound Firewall Rules

Egresser is a tool to enumerate outbound firewall rules, designed for penetration testers to assess whether egress filtering is adequate from within a corporate network. Probing each TCP port in turn, the Egresser server will respond with the client’s source IP address and port, allowing the client to determine whether or not the outbound port is permitted (both on IPv4 and IPv6) and to assess whether NAT traversal is likely to be taking place.

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  • Penetration testing
  • Tools and techniques

Testing .NET MVC For JSON Request XSS - POST2JSON Burp Extension

During a recent application penetration test on behalf of a client, one of the security vulnerabilities discovered was a stored cross-site scripting vector, delivered via a JSON request to a MVC3 controller. The malicious data (in this case a simple script tag proof-of-concept) was written to the database and subsequently echoed back to the user when viewing a number of pages within the application. This is how we wrote Burp plugin to bypass the XSS safety nets in the .NET framework...

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  • Research
  • Tools and techniques

Shared Dictionary Compression Over HTTP (SDCH) - Bypassing Your Filtering Devices

Following Cyberis’ recent articles on bypassing perimeter filtering devices (e.g. proxies, IDS and next-generation firewalls) by manipulating HTTP response headers, we’ve taken a closer look at some more obscure Content-Encoding mechanisms. This article discusses Shared Dictionary Compression over HTTP (SDCH), and the implications for perimeter security controls designed to protect your network from unwanted content.

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  • Tools and techniques

Update To ResponseCoder

Our HTTP Response manipulation tool - ResponseCoder - has been updated to allow manipulation of the HTTP version. Grab an updated copy.

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  • Tools and techniques

ResponseCoder - Manipulation Of HTTP Response Headers

ResponseCoder is designed to allow you to easily manipulate HTTP response headers - specifically to identify weaknesses in perimeter filtering appliances such as web proxies and next generation firewalls. It’s an open source PHP script that formulates HTTP response headers on-the-fly, allowing the operator to form specific test cases as necessary.

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  • Penetration testing
  • Tools and techniques

Finding Hidden Vhosts

During a recent test we observed a number of web servers that had a number vhosts configured, only some of which were discoverable from public DNS records. Internal DNS servers were configured to resolve the remaining ‘hidden’ vhosts served by the web server. Here's how we found them...

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  • Tools and techniques

Loading UDF Files On MySQL 5

Command execution via SQL injection is rarely possible on MySQL 5, as specifying the path to a shared library is not permitted due to security concerns - in other words it is not possible to create a UDF allowing you to run shell commands. Normally, if you can write to the default plugins location (/usr/lib/mysql/plugin), you already have root privileges and it's already game over. With MySQL 4 you could specify the full path to a shared library, so the install of a dangerous function was relatively straightforward. Before giving up altogether however, check to see if you can write to the defined plugin_dir directory...

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