New Spectre Vulnerability Version Beats All Mitigations, Performance to Badly Degrade After the Fix | TechPowerUp
 
Researches from the University of Virginia and University of California San Diego have published their latest case study. The two universities have worked hard to discover a new Spectre vulnerability variant that can pass all of the existing Spectre mitigations and exploit all of the existing processors coming from Intel and AMD. The vulnerability exploits all of the existing x86 processors, and as it is new, there are not implementations of hardware mitigation. The whitepaper called "I see dead μops" takes the implementation of exploiting micro-op caches that could lead to a potential data leak in the processor, which is leading to a Spectre-type exploit.

Modern x86 processors break down complex instructions into smaller RISC-like units called micro-ops, in the frontend, where it makes the design of the backend part much simples. The micro-ops are stored in the micro-ops cache. The paper is describing micro-op cache-based timing channel exploits in three primary settings: "a) across code regions within the same thread, but operating at different privilege levels, (b) across different co-located threads running simultaneously on different SMT contexts (logical cores) within the same physical core, and (c) two transient execution attack variants that leverage the micro-op cache to leak transiently accessed secrets, bypassing several existing hardware and software-based mitigations, including Intel's recommended LFENCE."
 
For more details about the ways of exploiting the data, it is recommended to read the paper in full. However, if you are wondering about the possible mitigations of this exploit, there could be some bad news regarding performance. Both Intel and AMD have been informed about the attack, and the solution is coming our way. However, since the exploit targets a low-level caching structure, a possible solution would take a severe degradation of performance, as believed by researchers. Maybe Intel and AMD find a solution that is not as severe, but rather a modest one. We must wait to find out.
 
It will be interesting to see what Intel and AMD come up with to combat this new vulnerability with degrading performance.