The Heartbleed flaw might represent a real risk to 150 million Android users, not because they're using a vulnerable version of Android, but rather because they are running a vulnerable app. That's a new finding from security firm FireEye, based on an examination of code running in Android apps.

The Heartbleed flaw is a vulnerability in the open-source OpenSSL cryptographic library that provides Secure Sockets Layer (SSL) data transport encryption. The Heartbleed flaw was first publicly reported on April 7 and has continued to be a serious concern ever since. Among the reasons for Heartbleed's broad impact is the fact that OpenSSL is widely used on servers and embedded devices, as well as the Google Android mobile operating system. Google has patched multiple versions of Android to protect against Heartbleed though Android 4.1 (Jelly Bean) still remains at risk. FireEye's analysis, however didn't focus on the native operating system.

According to FireEye, Android apps can often bypass the operating system's libraries for cryptography and use their own native OpenSSL libraries, which may not have been patched. Even though an app may be connecting to a secure, patched server, if the app itself uses a vulnerable version of OpenSSL, the connection is still insecure, Hui Xue, senior engineer at FireEye told eWEEK.

FireEye scanned approximately 54,000 apps on April 10 and found some 220 million downloads to be at risk from Heartbleed. FireEye notified the affected app developers, and by April 17, the number of at-risk downloads stood at 150 million.

To add further insult to injury for end users, FireEye found that apps that claim to scan for the Heartbleed flaw on Android, for the most part, don't really work. Looking at 17 different apps that claim to scan for Heartbleed, FireEye found that 11 of them did not scan apps for the Heartbleed flaw.

Going a level deeper, looking at the six that did scan for Heartbleed, two of them did not correctly identify apps that were in fact vulnerable to Heartbleed.

"Only two of them did a decent check on Heartbleed vulnerability of apps," FireEye researchers noted in a blog post. "We've also seen several fake Heartbleed detectors in the 17 apps, which don't perform real detections nor display detection results to users and only serve as adware."

While the risk to Android apps is nontrivial and should be taken seriously, attacks against Android apps are not happening—yet.

"We haven't observed active exploits yet, but given the scale, it's important for Android users to be aware of the ongoing threat," Xue said.

Sean Michael Kerner is a senior editor at eWEEK and InternetNews.com. Follow him on Twitter @TechJournalist.