New Spectre-Related 'Medium Severity' Flaw Patched in Linux Kernel

"The Spectre vulnerability that has haunted hardware and software makers since 2018 continues to defy efforts to bury it," reports the Register:On Thursday, Eduardo (sirdarckcat) Vela Nava, from Google's product security response team, disclosed a Spectre-related flaw in version 6.2 of the Linux kernel. The bug, designated medium severity, was initially reported to cloud service providers - those most likely to be affected - on December 31, 2022, and was patched in Linux on February 27, 2023. "The kernel failed to protect applications that attempted to protect against Spectre v2, leaving them open to attack from other processes running on the same physical core in another hyperthread," the vulnerability disclosure explains. The consequence of that attack is potential information exposure (e.g., leaked private keys) through this pernicous problem.... Spectre v2 - the variant implicated in this particular vulnerability - relies on timing side-channels to measure the misprediction rates of indirect branch prediction in order to infer the contents of protected memory. That's far from optimal in a cloud environment with shared hardware... The bug hunters who identified the issue found that Linux userspace processes to defend against Spectre v2 didn't work on VMs of "at least one major cloud provider."

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