CVE-2019-19338

A flaw was found in the fix for CVE-2019-11135, the way Intel CPUs handle speculative execution of instructions when a TSX Asynchronous Abort (TAA) error occurs. When a guest is running on a host CPU affected by the TAA flaw (TAA_NO=0), but is not affected by the MDS issue (MDS_NO=1), the guest was to clear the affected buffers by using a VERW instruction mechanism. But when the MDS_NO=1 bit was exported to the guests, the guests did not use the VERW mechanism to clear the affected buffers. This issue affects guests running on Cascade Lake CPUs and requires that host has 'TSX' enabled. Confidentiality of data is the highest threat associated with this vulnerability.

For additional information, please refer to the Red Hat Knowledgebase article: https://access.redhat.com/solutions/tsx-asynchronousabort

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Please refer to the Red Hat Knowledgebase Transactional Synchronization Extensions (TSX) Asynchronous Abort article (https://access.redhat.com/solutions/tsx-asynchronousabort) for mitigation instructions.