NEW TONTOU CPU ATTACK BYPASSES SPECTRE V2 FIXES TO LEAK LINUX PASSWORD HASHES

Summary from the TLDR InfoSec newsletter

Researchers at MIT CSAIL discovered a new branch predictor exploit that bypasses neutralization-based mitigations for Spectre v2 attacks. These mitigations assume that an attacker cannot exploit the time between when the branch predictor is isolated and when it is used by the victim branch. However, the researchers introduced a new primitive that can re-poison the CPU's state in this gap. The researchers demonstrated that this vulnerability can be exploited by users with unprivileged code execution on commodity hardware to extract /etc/shadow at a rate of 5.46 bytes/second.