What you need to know about the CoreText exploit that can crash iOS and OS X apps

What you need to know about the CoreText exploit that can crash iOS and OS X apps

An exploit in CoreText, the font rendering framework in current, publicly available versions of iOS and OS X, has been discovered that can cause apps to crash. According to habrahabr.ru, it can be remotely triggered via SMS or iMessage, Safari, and even the ESSID of a Wi-Fi network when scanning for and displaying them. Our security editor, Nick Arnott, has been looking into it this morning and shared the following:

  • OS X 10.8.4 - Receiving the string in iMessage will crash it. You can restart iMessage without it crashing and delete the conversation.
  • OS X Mavericks - Doesn't crash Messages or Safari.
  • iOS 7 - Doesn't crash Messages or Safari.
  • iOS 6 - System crashes after receiving message. After rebooting, Messages will crash every time you try to open it.

Here's his workaround for iOS 6:

If you receive a new message from somebody (who didn't send the offending text) you can tap to open that message directly. You will be able to access this message and respond to that person. If the person who send the offending message sends you enough messages to push the offending one off the screen, you will also be able to open messages from them from an alert to respond, but scrolling up will crash. In all cases trying to go back to the main list of messages will crash. A workaround for this is to sign out of iMessage, sign in to a different account, sign out, then sign back in with your original account. This will remove any previous messages you had on the device.

Also, that clearing of message history may require you to view or delete the offending message on another device (iOS 7 device or OS X) to ensure that it doesn't show up when you sign back in to iMessage.

You can also continue to send new messages to people from the Contacts or Photos app.

Apple is apparently aware of the exploit and is rumored to have already fixed it in Mavericks as well as iOS 7. There's also reportedly a jailbreak patch for it.

In the meantime, just like the previous FIle:/// exploit that caused crashes on OS X, it probably won't amount to much cause for real-world concern. Unless you have friends who are complete dicks and would delight in messing with you this way, or unless and until there are wide spread reports of this exploit turning up in the wild, it's probably not worth spending much time worrying about.

Nick Arnott contributed significantly to this article.

Source: habrahabr.ru

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Rene Ritchie

EiC of iMore, EP of Mobile Nations, Apple analyst, co-host of Debug, Iterate, Vector, Review, and MacBreak Weekly podcasts. Cook, grappler, photon wrangler. Follow him on Twitter and Google+.

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Reader comments

What you need to know about the CoreText exploit that can crash iOS and OS X apps


+1 to last paragraph. Once again, the blogosphere is going to blow it all out of proportion - because they can... and they're being complete dicks.

I agree. I'm sure our local news, after running out of stories about house fires, high school football, and magic donuts, will have this in their "Tech Spotlight", which is anything but.

Since it is a bug in the core font rendering system, anything that displays a specifically formatted string can crash - from a web page to scanning for WiFi or BT networks, and everything in between. It's a severe bug, but, as Rene suggests, it is not one that you are likely to encounter.

Though, if the linked article is correct and Apple was notified of this 6 months ago and has not patched it, that would be worrisome. Everybody has bugs -- how and how fast you react to them is what is most important.