Intel on Tuesday pushed microcode updates to fix a high-severity CPU bug that has the potential to be maliciously exploited against cloud-based hosts.
The flaw, affecting virtually all modern Intel CPUs, causes them to “enter a glitch state where the normal rules don’t apply,” Tavis Ormandy, one of several security researchers inside Google who discovered the bug, reported. Once triggered, the glitch state results in unexpected and potentially serious behavior, most notably system crashes that occur even when untrusted code is executed within a guest account of a virtual machine, which, under most cloud security models, is assumed to be safe from such faults. Escalation of privileges is also a possibility.
Very strange behavior
The bug, tracked under the common name Reptar and the designation CVE-2023-23583, is related to how affected CPUs manage prefixes, which change the behavior of instructions sent by running software. Intel x64 decoding generally allows redundant prefixes—meaning those that don’t make sense in a given context—to be ignored without consequence. During testing in August, Ormandy noticed that the REX prefix was generating “unexpected results” when running on Intel CPUs that support a newer feature known as fast short repeat move, which was introduced in the Ice Lake architecture to fix microcoding bottlenecks.
To provide the best experiences, we use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us to process data such as browsing behavior or unique IDs on this site. Not consenting or withdrawing consent, may adversely affect certain features and functions.
Functional
Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes.The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.
