A flaw was found in the fix for CVE-2019-11135, in the Linux upstream kernel versions before 5.5 where, 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.
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.
| Link | Tags |
|---|---|
| https://www.openwall.com/lists/oss-security/2019/12/10/3 | mailing list third party advisory patch |
| https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-19338 | issue tracking third party advisory patch |
| https://software.intel.com/security-software-guidance/insights/deep-dive-intel-transactional-synchronization-extensions-intel-tsx-asynchronous-abort | third party advisory |