Second HTTPS snooping flaw breaks security for thousands of iOS apps

The vulnerability stems from a failure to validate the domain names of digital certificates in AFNetworking, a library used by a large number of iOS and Mac OS X app developers to implement Web communications -- including those over HTTPS (HTTP with SSL/TLS encryption).

The flaw allows attackers in a position to intercept HTTPS traffic between a vulnerable application and a Web service to decrypt it by presenting the application with a digital certificate for a different domain name. Such man-in-the-middle attacks can be launched over insecure wireless networks, by hacking into routers or through other methods.

According to a company called SourceDNA, which tracks the use of third-party components in mobile apps, more than 25,000 iOS applications are potentially vulnerable because they use AFNetworking 2.5.2 or older versions.

The vulnerability was fixed in AFNetworking 2.5.3, released on April 20.

Applications that have certificate pinning turned on are not vulnerable, but this mechanism is only used by a small number of developers, SourceDNA said Friday in a blog post.

One interesting aspect of this flaw is that it was reported to the AFNetworking developers on March 27, one day after a different flaw that allowed HTTPS snooping was addressed in AFNetworking 2.5.2.

That vulnerability only existed in AFNetworking 2.5.1, released on Feb. 9, and it ended up affecting 1,000 of the over 100,000 iOS apps that use AFNetworking. The new flaw renders apps that use older versions of the library vulnerable as well, as long as they rely on AFNetworking for establishing HTTPS connections to Web servers.

SourceDNA set up an online service called Searchlight that can be used by users to manually check if the iOS apps installed on their devices are vulnerable. The service shows that apps from large developers like Microsoft, Yahoo and Google are potentially affected by the AFNetworking flaws.