A Flash Exploit (CVE-2015-5119) From the Hacking Team Leak

***Update July 12, 2015--It was recently discovered that Hacking Team possessed an additional zero-day exploit for Adobe Flash--CVE-2015-5122. CVE-2015-5122 was patched by Adobe on July 8, 2015. While a different exploit than CVE-2015-5119 discussed below, Trustwave SWG customers are also protected against CVE-2015-5122 out of the box without any additional updates.***

Hacking Team is a company based in Italy that "provide[s] effective, easy-to-use offensive technology to the worldwide law enforcement and intelligence communities." They sell tools, such as the RCS (Remote Control System) – a high end grade Trojan. They also market exploits that allow for the compromise of remote computers. A recent breach of Hacking Team's systems has revealed a trove of data and allowed security researchers to examine the arsenal developed by the team over the years. While this post isn't commentary on their data breach, we examine a new exploit that has come to light following the compromise.

Examining the leaked "Windows-Multi-Browser" package reveals a well documented and automated exploit kit. It leverages two zero day exploits – one for Adobe Flash (now assigned CVE-2015-5119) and a privilege escalation exploit for Windows. When combined it creates a very powerful infection mechanism. The package also includes another Flash exploit (CVE-2015-0349) which was patched after VUPEN used it in Pwn2Own 2015. However, the leak contains evidence that this exploit was used as early as 2013 and was actually a zero day exploit for at least two years.

What is particularly interesting about this package is the fact that Hacking Team relied on a single remote code execution (RCE) exploit and a single elevation of privilege (EoP) exploit to achieve full compromise via different vectors. It also allowed for the creation of throw-away web servers hosting the exploit kit, which can serve an HTML page that compromises the victim via the browser (both Internet Explorer and Firefox are supported). But additionally it could serve a Microsoft Office file (Word, PowerPoint and Excel are all supported) based on the same Flash exploit.

Office.Flash.OCX

Such an Office file could easily be sent over email and infect victims that maybe wouldn't be easily convinced to click on a suspicious link. But with some clever social engineering, the same victim might be convinced to open an Office document.

Once such a document is opened, Microsoft Office will dynamically pull and load the Flash object from a remote server to exploit the victim machine. After the initial code execution is achieved, the second stage kicks in to leverage the EoP exploit and gain full control over the system by installing a Trojan (usually the RCS Trojan developed by Hacking Team) with the highest privileges on the PC.

Office.Flash.Fiddler

One more interesting artifact that we noticed inside the leaked package is a simple web interface (presumably provided for customers as the evidence suggests it was deployed on a public server, rather than in internal resource), for an all-in-one easy generation interface for the various exploits. All you need to do is supply the executable (a payload) that will be installed on the victim machine.

Screen Shot 2015-07-08 at 4.50.00 PM

This method of leveraging a single RCE exploit into multiple vectors shows how powerful a single zero day can be, and how dangerous it could be in malicious hands.

By now most of the criminal exploit kits out there had already integrated this exploit, but Trustwave SWG customers needn't worry. We tested real-world samples recovered from the leaked data and found that Trustwave SWG blocked the attack out of the box without any additional updates. Trustwave SWG also provides specific rules per exploit kit as an added security layer, stopping the attack regardless of the integrated exploits.

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