MeltdownPrime and SpectrePrime are the two new variant names.
From the Tom's Hardware article:
"Princeton and Nvidia researchers teamed up to produce a testing method that can generate code that represents the essence of an attack. More precisely, their method is CPU architecture-aware, so it emulates exactly what a software attack would translate into on the hardware level. According the the researchers, their tool can be used to quickly generate a set of 'security litmus tests' for a class of security exploits."
"In the process of their testing, they discovered that the speculative execution methods that are exploited by the Meltdown and Spectre vulnerabilities leave a trail that might not be observable in only a CPU's shared cache, but in its cores' individual caches as well."
"What the researchers discovered is that, because certain caches might be partially mirrored across cores, the effects of speculative execution occurring on one core can be detectable on another core. Test cases exploiting this principle created by the researchers were able to recover hidden data at 99.95% accuracy. By comparison, their test cases of a traditional Spectre exploit only reached 97.9% accuracy."
"[...] the researchers said that current software-based Meltdown/Spectre mitigations seem successful in blocking their new exploits. However, these exploits will likely need their own distinct fix, different from those for traditional Spectre, if they are to be mitigated in hardware."
http://www.tomshardware.com/news/new-variants-meltdown-spect...
https://arxiv.org/pdf/1802.03802.pdf
TL;DR:
MeltdownPrime and SpectrePrime are the two new variant names.
From the Tom's Hardware article:
"Princeton and Nvidia researchers teamed up to produce a testing method that can generate code that represents the essence of an attack. More precisely, their method is CPU architecture-aware, so it emulates exactly what a software attack would translate into on the hardware level. According the the researchers, their tool can be used to quickly generate a set of 'security litmus tests' for a class of security exploits."
"In the process of their testing, they discovered that the speculative execution methods that are exploited by the Meltdown and Spectre vulnerabilities leave a trail that might not be observable in only a CPU's shared cache, but in its cores' individual caches as well."
"What the researchers discovered is that, because certain caches might be partially mirrored across cores, the effects of speculative execution occurring on one core can be detectable on another core. Test cases exploiting this principle created by the researchers were able to recover hidden data at 99.95% accuracy. By comparison, their test cases of a traditional Spectre exploit only reached 97.9% accuracy."
"[...] the researchers said that current software-based Meltdown/Spectre mitigations seem successful in blocking their new exploits. However, these exploits will likely need their own distinct fix, different from those for traditional Spectre, if they are to be mitigated in hardware."