Google Android Master Key Vulnerability Exploit Code Circulates

Proof-of-concept code for exploiting a Google Android master key vulnerability that can be used to Trojanize legitimate apps is making the rounds on the Internet.

The exploit, built by viaForensics mobile security engineer Pau Oliva Fora, takes advantage of a vulnerability uncovered by Bluebox Security. Last week, Bluebox researchers revealed general details of the vulnerability, which is slated to be described in detail at the upcoming Black Hat conference in Las Vegas.

The flaw – discussed here in a podcast with Bluebox co-founder Adam Ely – can be used to turn legitimate applications in Trojans, and has been present since at least Android 1.6 – making it roughly four years old.

The vulnerability has to do with how Android verifies the digital signatures of applications. If exploited, an attacker could modify the applications without breaking the signature itself.  After Bluebox discussed the vulnerability at a high-level last week, developers of CyanogenMod – a customized, aftermarket firmware distribution for Android – were able to discover more details of the bug.

Afterwards, Oliva Fora was able to develop an exploit, which he released on GitHub. On Twitter, Oliva Fora noted that he only went public with the exploit code after details of the vulnerability had already been released.  

Google has pushed out a patch for Google Android to fix the vulnerability, and Google Play scans for the issue. Google’s Verification Tool is also able to offer protection for Android users who download their apps from other app stores. Some of the company’s OEM partners, such as Samsung, are already shipping a fix to their Android devices, Google told SecurityWeek.

So far, Google has seen no evidence via its security scanning tools that the vulnerability being exploited.