In June 2021, two new vulnerabilities, Speculative Code Store Bypass (SCSB, CVE-2021-0086) and Floating Point Value Injection (FPVI, CVE-2021-0089), affecting all modern x86-64 CPUs both from Intel and AMD were discovered. In order to mitigate them software has to be rewritten and recompiled. ARM CPUs are not affected by SCSB but some certain ARM architectures are affected by FPVI. In August 2021 a vulnerability called "Transient Execution of Non-canonical Accesses" affecting certain AMD CPUs was disclosed. It requires the same mitigations as the MDS vulnerability affecting certain Intel CPUs. It was assigned CVE-2020-12965. Since most x86 software is already patched against MDS and this vulnerability has the exact same mitigations, software vendors don't have to address this vulnerability. In October 2021 for the first time ever a vulnerability similar to Meltdown was disclosed to be affecting all AMD CPUs however the company doesn't think any new mitigations have to be applied and the existing ones are already sufficient. In March 2022, a new variant of the Spectre vulnerability called Branch History Injection was disclosed. It affects certain ARM64 CPUs and the following Intel CPU families: Cascade Lake, Ice Lake, Tiger Lake and Alder Lake. According to Linux kernel developers AMD CPUs are also affected. In March 2022, a vulnerability affecting a wide range of AMD CPUs was disclosed under CVE-2021-26341. In June 2022, multiple MMIO Intel CPUs vulnerabilities related to execution in virtual environments were announced. The following CVEs were designated: CVE-2022-21123, CVE-2022-21125, CVE-2022-21166. In July 2022, the Retbleed vulnerability was disclosed affecting Intel Core 6 to 8th generation CPUs and AMD Zen 1, 1+ and 2 generation CPUs. Newer Intel microarchitectures as well as AMD starting with Zen 3 are not affected. The mitigations for the vulnerability decrease the performance of the affected Intel CPUs by up to 39%, while AMD CPUs lose up to 14%. In August 2022, the SQUIP vulnerability was disclosed affecting Ryzen 2000–5000 series CPUs. According to AMD the existing mitigations are enough to protect from it. According to a Phoronix review released in October, 2022 Zen 4/Ryzen 7000 CPUs are not slowed down by mitigations, in fact disabling them leads to a performance loss. In February 2023 a vulnerability affecting a wide range of AMD CPU architectures called "Cross-Thread Return Address Predictions" was disclosed. Future Spectre class vulnerabilities will remain unfixed because otherwise CPU designers will have to disable speculative execution which will entail