CVE-2022-21166: 
vulnerability analysis and mitigation

CVE-2022-21166 is a vulnerability discovered in Intel processors related to incomplete cleanup in specific special register write operations. The vulnerability was disclosed in June 2022 and affects various Intel processor models. When successfully exploited, this vulnerability allows an authenticated user to potentially enable information disclosure via local access (Intel SA, NVD).

The vulnerability is part of the MMIO Stale Data vulnerabilities family, which is similar to previously published Microarchitectural Data Sampling (MDS) issues. It specifically relates to incomplete cleanup during specific special register write operations. The vulnerability has been assigned a CVSS v3.1 base score of 5.5 (MEDIUM) with the vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N, indicating local access is required for exploitation (NVD, Xen Advisory).

The vulnerability can lead to information disclosure, potentially allowing attackers to read sensitive data from other security contexts in the system. This can include data belonging to other VMs or to the hypervisor itself. The impact varies depending on the CPU model and system configuration (Xen Advisory, NetApp Advisory).

Mitigation requires functionality added in the IPU 2022.1 (May 2022) microcode release from Intel. For systems where less privileged domains have MMIO mappings of affected endpoints, the 'spec-ctrl=unpriv-mmio' option can be enabled to mitigate cross-domain fill buffer leakage and extend SRBDS protections. Various operating system vendors have released kernel updates incorporating these mitigations (Debian Advisory, Xen Advisory).