CVE-2023-1998

Name of the Vulnerable Software and Affected Versions Linux kernel version 6.2

Description The Linux kernel allows userspace processes to enable mitigations by calling prctl with PR SET SPECULATION CTRL, which disables the speculation feature as well as by using seccomp. However, on VMs of at least one major cloud provider, the kernel still left the victim process exposed to attacks in some cases even after enabling the spectre-BTI mitigation with prctl. This happened because when plain IBRS was enabled, the kernel had some logic that determined that STIBP was not needed. The IBRS bit implicitly protects against cross-thread branch target injection. However, with legacy IBRS, the IBRS bit was cleared on returning to userspace, due to performance reasons, which disabled the implicit STIBP and left userspace threads vulnerable to cross-thread branch target injection against which STIBP protects.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.