A bug in Apple’s WebView allow an attacker to initiate phone calls without user confirm

Twitter and LinkedIn iOS apps are vulnerable!

The security researcher Collin Mulliner has discovered an exploitable vulnerability in Apple’s WebView that could allow phone calls to a number of the attacker’s choosing.

iOS WebViews can be used to automatically call an attacker controlled phone number. The attack can block the phone’s UI for a short amount of time and therefore prevent the victim from canceling the call. The bug is an application bug that likely is due to bad OS/framework defaults. One major issue with this vulnerability is that it is really easy to exploit. App developers have to fix their code as soon as possible.

Mulliner said the vulnerability is trivial to exploit, requiring at a minimum one line of HTML code and iOS developers who have embedded Apple’s WebView into mobile apps need to be aware.

The risks to the user include calls to to premium numbers or denial-of-service against telephone numbers of public services:

About a week agoI read an news post about a guy who got arrested for accidentally DoSing 911 by creating a web page that automatically dialed 911 when visited it from an iPhone. This was most likely due to a bug with the handling of TEL URI. I immediately thought about a bug I reported to Apple in late October 2008 . I couldn’t believe this bug has resurfaced so I investigated. The article said something about posting links on Twitter.

The researcher has also published two video demonstration of the exploit:

 


References

https://www.mulliner.org/blog/blosxom.cgi/security/ios_webview_auto_dialer.html

 

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