A recently disclosed vulnerability in Apple’s iOS operating system has sent shockwaves through the cybersecurity community, revealing that a single line of code could effectively “soft-brick” iPhones-rendering them unusable until a full device restore is performed.
The flaw, now tracked as CVE-2025-24091, was addressed by Apple in the iOS 18.3 update, but its simplicity and potential for widespread disruption have raised serious concerns among users and security experts alike.
The Exploit: Darwin Notifications and System-Wide Chaos
The vulnerability centers on the legacy Darwin notification system, a low-level public API used for inter-process communication across Apple’s platforms.
Unlike higher-level notification centers, Darwin notifications required no special privileges for sending or receiving messages, making them accessible to any app running on the device-even those operating within the tight confines of the iOS sandbox.
Security researcher analysis revealed that certain system processes, including SpringBoard (the iOS home screen manager), were listening for specific Darwin notifications to trigger critical system behaviors. By sending a single, specially crafted notification as:
swiftnotify_post("com.apple.MobileSync.BackupAgent.RestoreStarted")
An unprivileged app could force the device into a “Restore in Progress” state.
This would display a system UI indicating that a device restore was underway, but with no actual restore occurring, the process would fail and prompt the user to restart.
Upon reboot, the malicious code could be triggered again, trapping the device in a persistent denial-of-service loop.
The only escape: a full device erase and restore from backup.
Proof of Concept and Real-World Impact
The proof of concept, dubbed “EvilNotify,” demonstrated that not only could this attack be launched from a foreground app, but it could also be embedded in widget extensions processes that iOS is eager to execute in the background.
By crashing the extension after sending the notification, the system would repeatedly attempt to relaunch it, perpetuating the attack even across device reboots.
Other potential disruptions included:
- Blocking system-wide gestures (Control Center, Notification Center, Lock Screen)
- Forcing the device to disregard Wi-Fi in favor of cellular data
- Triggering security prompts and UI elements intended for legitimate system operations
Apple’s Response and Mitigation
Apple responded by introducing a new entitlement system, restricting the ability to send sensitive Darwin notifications only to trusted, system-signed processes.
As of iOS 18.3, attempts by unauthorized apps to send these notifications are blocked, effectively neutralizing this attack vector.
User Guidance
Users are strongly urged to update their devices to iOS 18.3 or later to ensure protection against this and other actively exploited vulnerabilities.
Apple’s swift response underscores the importance of timely software updates in maintaining device security.
This vulnerability highlights how legacy features, when left unchecked, can pose significant risks even in tightly controlled environments like iOS.
With a single line of code, attackers could have rendered millions of devices inoperable-until Apple’s latest patch closed the door for good.
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