Kaspersky’s Global Research and Analysis Team (GReAT) has exposed a previously unknown “feature” in Apple iPhones that allowed malware to bypass hardware-based memory protection.

Addressed as CVE-2023-38606, which was patched in July 2023, the issue affected iPhones running iOS versions up to 16.6, according to the cybersecurity outfit this week.

Kaspersky reckons the hardware feature (technical details here) may have been intended for testing or debugging. Yeah, hopefully that. Certainly, the GReAT gang couldn’t find any public documentation on it, which meant the attack vector proved tricky to detect and analyze using the team’s usual tools when miscreants came to exploit the hole.

According to Kaspersky, “attackers leveraged this hardware feature to bypass hardware-based security protections and manipulate the contents of protected memory regions.”

Researchers had to reverse-engineer the device to track down the vulnerability exploited. Particular attention was paid to Memory-Mapped IO (MMIO) addresses used for communication between the CPU and other devices. The problem was that the attackers used unknown MMIO addresses to bypass hardware-based kernel protection. Therefore, the team had to pick through the hardware, firmware, and kernel images to work out what was going on.

“This is no ordinary vulnerability,” said Boris Larin, Principal Security Researcher at Kaspersky’s GReAT.

“Due to the closed nature of the iOS ecosystem, the discovery process was both challenging and time-consuming, requiring a comprehensive understanding of both hardware and software architectures. What this discovery teaches us once again is that even advanced hardware-based protections can be rendered ineffective in the face of a sophisticated attacker, particularly when there are hardware features allowing to bypass these protections.”

The vulnerability played a critical role in the “Operation Triangulation” campaign earlier this year, which allowed miscreants to gain access to targeted devices, deploy spyware, and snoop user data. Kaspersky informed Apple about the exploitation of the hardware feature, which was swiftly mitigated.

However, as Larin observed, all the hardware protections in the world won’t help if somebody leaves in an undocumented something that allows those protections to be bypassed. ‘Security through obscurity’ just doesn’t cut it anymore.