iPhone Users: Beware of Unfamiliar WiFi Networks…


June 28, 2021

iPhone Users: Beware of Unfamiliar WiFi Networks...

There’s a general rule of thumb that says you shouldn’t join a WiFi network you don’t know. A new iPhone issue helps prove the point.

Here’s the skinny: if you join a WiFi network with a name like “%p%s%s%s%s%n” will royally mess up your device’s ability to connect to the internet.

The issue was discovered by a software engineer named Carl Schou. Schou claims to have uncovered the bug by accident, and nothing he did seemed to restore functionality. Thankfully, after a bit of head-scratching, Schou was able to reset his phone’s network settings and regain full functionality. We’ve posted instructions regarding how you too can reset your network functionality, but first, I want to talk a bit about why this could be a major issue going forward for iOS devices.

Why is this happening?

Security researchers who’ve analyzed crash reports associated with the bug believe it’s a parsing issue. If a “%” sign is used in a WiFi network name, iOS can’t interpret it correctly and identifies the “%” as something called a “string-format specifier” when it’s not.

A “string format specifier” is used in C and other C-type languages. They’re typically processed as a variable name or command and not as text.

When asked by Bleeping Computer why Schou formatted his WiFi’s SSID after a format string because it “f***** with poorly developed devices.” It would seem Apple’s iOS and iPhone would fall in that category by Schou’s definition.

Should you be worried?

No, not really. I mean, the opening paragraph of this very article tells you you shouldn’t be joining any WiFi networks you’re not familiar with as there’s a risk you’ll potentially expose sensitive information. It doesn’t look like there’s any way for malicious actors to leverage this new bug to steal PII data.

However, not all cyberthugs are interested in stealing information. Some are only interested in ruining their target’s day. And borking an iPhone’s ability to connection to the internet is a great way of accomplishing that.

How do you fix the problem?

It’s really easy to fix this. All you have to do is the following:

  1. Go to Settings on your iPhone
  2. Select General
  3. Under General look for Reset. It’s towards the bottom of the menu
  4. Once on the Reset screen select the Reset Network Settings option
  5. Confirm you do want to reset your network settings. Your device will start and your problems should be fixed
  6. Don’t join any more unknown WiFi networks

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Carl Keyser is the Content Manager at Integris.

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