September 10, 2025
Apple Security Engineering and Architecture (SEAR) has unveiled Memory Integrity Enforcement (MIE), an always-on, hardware-assisted memory safety technology designed to block entire classes of memory corruption vulnerabilities across iPhone devices. Apple calls MIE “the most significant upgrade to memory safety in the history of consumer operating systems.”
Apple highlights that the project was the result of “an unprecedented design and engineering effort, spanning half a decade, that combines the unique strengths of Apple silicon hardware with our advanced operating system security to provide industry-first, always-on memory safety protection across our devices — without compromising our best-in-class device performance.”
The effort builds on Apple’s earlier work with secure memory allocators like kalloc_type and xzone malloc, and the hardware-backed Pointer Authentication Codes (PAC) introduced in the A12 Bionic chip.
At the core of MIE is Arm’s Enhanced Memory Tagging Extension (EMTE), which Apple adapted and extended. While standard MTE could be configured in asynchronous mode — leaving race windows attackers might exploit — Apple rejected this approach. As the blog explains: “We believe memory safety protections need to be strictly synchronous, on by default, and working continuously.”
By integrating EMTE in synchronous mode, backed with Tag Confidentiality Enforcement and typed memory allocators, Apple created a system that blocks buffer overflows, use-after-free exploits, and other memory corruption attacks before they can take hold.
Apple emphasizes that while the vast majority of users will never face such threats, MIE is primarily designed to counter mercenary spyware. The blog notes: “There has never been a successful, widespread malware attack against iPhone. The only system-level iOS attacks we observe in the wild come from mercenary spyware… exploit chains that cost millions of dollars to target a very small number of specific individuals and their devices.”
These spyware campaigns rely heavily on memory corruption vulnerabilities. By cutting off exploitability at the hardware and allocator level, MIE makes such attacks vastly more difficult and expensive to execute.
Unlike Google’s optional MTE mode on Android, Apple’s design integrates hardware and operating system security more deeply. SEAR explains: “Our mission with Memory Integrity Enforcement is to protect all users by default… [with] an extensive combination of features not present in other MTE implementations.”
Importantly, Apple claims this protection comes “while maintaining the power and performance that users expect”, thanks to silicon-level optimization of EMTE workloads.
Apple’s offensive research team stress-tested MIE against historic and modern exploit chains. According to SEAR: “Both approaches revealed the same conclusion: Memory Integrity Enforcement vastly reduces the exploitation strategies available to attackers… Even with substantial effort, we could not rebuild any of these chains to work around MIE.”
With Memory Integrity Enforcement debuting on the iPhone 17 and iPhone Air, Apple has set a new standard for consumer device security. By embedding memory tagging and confidentiality protections directly into Apple silicon and operating systems, MIE represents a major leap forward — one that could reshape attacker economics and render decades of exploit techniques obsolete.
As SEAR concludes, “Because of how dramatically it reduces an attacker’s ability to exploit memory corruption vulnerabilities on our devices, we believe Memory Integrity Enforcement represents the most significant upgrade to memory safety in the history of consumer operating systems.”
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