Late on Thursday, Apple issued a new support document highlighting how the recently unearthed chip vulnerabilities involving Intel, ARM, and AMD processors impacts nearly the entirety of Apple’s product line. Specifically, Apple notes that all Macs and iOS devices are technically susceptible to Spectre and Meltdown, two vulnerabilities which could allow a malicious actor to access sensitive user data in protected memory. Apple, though, makes a point of emphasizing that no known exploits have been uncovered.
“All Mac systems and iOS devices are affected,” the support document reads, “but there are no known exploits impacting customers at this time. Since exploiting many of these issues requires a malicious app to be loaded on your Mac or iOS device, we recommend downloading software only from trusted sources such as the App Store.”
As for what Apple is doing to combat the vulnerabilities, which, interestingly enough, were discovered by security researchers at Google’s Project Zero, Apple relays that patches for the Meltdown vulnerability were already issued with the following updates: iOS 11.2, macOS 10.13.2, and tvOS 11.2. Incidentally, Apple notes that watchOS did not require a patch. Additionally, Apple maintains that the updates above have no discernible impact on system performance. This point is worth highlighting given that the original report from The Register claimed that the requisite patches could result in systems running as much as 30% slower.
With respect to the Spectre vulnerability, which Apple notes is “extremely difficult to exploit,” Apple says that iOS and Mac users can expect a patch relatively soon.
To this point, Apple notes:
Analysis of these techniques revealed that while they are extremely difficult to exploit, even by an app running locally on a Mac or iOS device, they can be potentially exploited in JavaScript running in a web browser. Apple will release an update for Safari on macOS and iOS in the coming days to mitigate these exploit techniques. Our current testing indicates that the upcoming Safari mitigations will have no measurable impact on the Speedometer and ARES-6 tests and an impact of less than 2.5% on the JetStream benchmark.
The entirety of Apple’s new support document can be read below:
About speculative execution vulnerabilities in ARM-based and Intel CPUs
Security researchers have recently uncovered security issues known by two names, Meltdown and Spectre. These issues apply to all modern processors and affect nearly all computing devices and operating systems. All Mac systems and iOS devices are affected, but there are no known exploits impacting customers at this time. Since exploiting many of these issues requires a malicious app to be loaded on your Mac or iOS device, we recommend downloading software only from trusted sources such as the App Store. Apple has already released mitigations in iOS 11.2, macOS 10.13.2, and tvOS 11.2 to help defend against Meltdown. Apple Watch is not affected by Meltdown. In the coming days we plan to release mitigations in Safari to help defend against Spectre. We continue to develop and test further mitigations for these issues and will release them in upcoming updates of iOS, macOS, tvOS, and watchOS.
Background
The Meltdown and Spectre issues take advantage of a modern CPU performance feature called speculative execution. Speculative execution improves speed by operating on multiple instructions at once—possibly in a different order than when they entered the CPU. To increase performance, the CPU predicts which path of a branch is most likely to be taken, and will speculatively continue execution down that path even before the branch is completed. If the prediction was wrong, this speculative execution is rolled back in a way that is intended to be invisible to software.
The Meltdown and Spectre exploitation techniques abuse speculative execution to access privileged memory—including that of the kernel—from a less-privileged user process such as a malicious app running on a device.
Meltdown
Meltdown is a name given to an exploitation technique known as CVE-2017-5754 or “rogue data cache load.” The Meltdown technique can enable a user process to read kernel memory. Our analysis suggests that it has the most potential to be exploited. Apple released mitigations for Meltdown in iOS 11.2, macOS 10.13.2, and tvOS 11.2. watchOS did not require mitigation. Our testing with public benchmarks has shown that the changes in the December 2017 updates resulted in no measurable reduction in the performance of macOS and iOS as measured by the GeekBench 4 benchmark, or in common Web browsing benchmarks such as Speedometer, JetStream, and ARES-6.
Spectre
Spectre is a name covering two different exploitation techniques known as CVE-2017-5753 or “bounds check bypass,” and CVE-2017-5715 or “branch target injection.” These techniques potentially make items in kernel memory available to user processes by taking advantage of a delay in the time it may take the CPU to check the validity of a memory access call.
Analysis of these techniques revealed that while they are extremely difficult to exploit, even by an app running locally on a Mac or iOS device, they can be potentially exploited in JavaScript running in a web browser. Apple will release an update for Safari on macOS and iOS in the coming days to mitigate these exploit techniques. Our current testing indicates that the upcoming Safari mitigations will have no measurable impact on the Speedometer and ARES-6 tests and an impact of less than 2.5% on the JetStream benchmark. We continue to develop and test further mitigations within the operating system for the Spectre techniques, and will release them in upcoming updates of iOS, macOS, tvOS, and watchOS.
