Ubuntu Security Notice 6396-3 - It was discovered that some AMD x86-64 processors with SMT enabled could speculatively execute instructions using a return address from a sibling thread. A local attacker could possibly use this to expose sensitive information. Daniel Moghimi discovered that some Intel Processors did not properly clear microarchitectural state after speculative execution of various instructions. A local unprivileged user could use this to obtain to sensitive information.
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