Researcher finds iPhone bug that disables wireless functionality after joining a WiFi network called “%p%s%s%s%s%n”; resetting network settings fixes the issue
here's the fix and how to prevent it Gordon Kelly / Forbes : Serious Warning Issued For Millions Of Apple iPhone Users Ali Salman / Wccftech : iOS Bug Causes Certain Network Name to Permanently Disable WiFi on iPhone Tweets: Carl Schou / @vm_call : After joining my personal WiFi with the SSID “%p%s%s%s%s%n”, my iPhone permanently disabled it's WiFi functionality. Neither rebooting nor changing SSID fixes it :~) https://twitter.com/... Carl Schou / @vm_call : Zhi has written a great technical write-up on the iOS WiFi SSID 0day https://twitter.com/... Kenn White / @kennwhite : “You're just being paranoid by taking a prepaid burner to DEF CON” https://twitter.com/... Patrick O'Sullivan / @insane_irish : @vm_call @NolanSIGBUS A QA engineer walks into a bar He orders a beer. Orders 0 beers. Orders 99999999999 beers. Orders a lizard. Orders -1 beers. Orders a ueicbksjdhd. First real customer walks in and asks where the bathroom is. The bar bursts into flames, killing everyone. https://www.reddit.com/... Kevin Beaumont / @gossithedog : New Guest Wi-Fi name. https://twitter.com/... Sam Stepanyan / @securestep9 : If you own an iPhone/iOS device - there is a #ZeroDay vulnerability out which breaks iPhone's #WiFi (almost) permanently. Beware of WiFi networks named %p%s%s%s%s%n - do not join/connect to them. Full technical explanation in article below: https://www.bleepingcomputer.com/ ... https://twitter.com/... Kevin Beaumont / @gossithedog : Analysis of the bug - yes, a format string vuln 🤣 https://blog.chichou.me/... Jaimyn / @jaimyn_m : @vm_call Can confirm this works with an open / unsecured WiFi network with that SSID, and that using the “reset network settings” feature fixes it. Neat find! It also completely breaks AirDrop! 🤣 https://twitter.com/...
Context & Ripple Effects
The disclosure showed that a malformed Wi‑Fi network name could leave an iPhone unable to use wireless networking until its network settings were reset. Apple’s subsequent iOS 14.7 beta fix for network names that disable Wi‑Fi turned the report from a user workaround into a software-maintenance issue.
Later coverage of a Private Wi‑Fi Address flaw that exposed real MAC addresses shows Apple’s Wi‑Fi stack continued to generate both reliability and privacy fixes, including under Lockdown Mode.
First-order effects
- iPhone users who join the named SSID lose Wi‑Fi functionality until they reset network settings, while avoiding that network name prevents the trigger.
- Apple must remediate input handling for Wi‑Fi network names; the related iOS 14.7 beta indicates that a fix entered testing soon after disclosure.
Second-order effects
- Network operators and users sharing Wi‑Fi credentials have a concrete reason to avoid malformed SSIDs, because a network name alone can disrupt an iPhone’s connectivity.
- Apple’s Wi‑Fi update cycle has to cover both network-name parsing and identifier privacy, as the later MAC-address fix demonstrates.
Third-order effects
- The recurring fixes point to wireless networking as a persistent platform-hardening surface: reliability failures and privacy leaks can arise before an app or web page is involved.
- If this pattern persists, Apple’s security posture will be judged increasingly on the resilience of default connectivity features, including protections advertised for higher-risk modes such as Lockdown Mode.
The trend: Apple’s iPhone security maintenance is expanding from application-facing defenses to the lower-level Wi‑Fi behaviors that determine whether devices can connect privately and reliably.