CVE-2023-46842: x86 HVM hypercalls may trigger Xen bug check

Vulnerability summary

CVE-2023-46842 is a medium (CVSS 6.5) vulnerability in fedoraproject fedora. EPSS estimates a 8.53% chance of exploitation in the next 30 days, higher than 95% of scored vulnerabilities.

Timeline

1. 16-05-2024
   PublishedVulnerability first disclosed.
2. 04-11-2025
   Last modifiedVulnerability information updated.

Description

Unlike 32-bit PV guests, HVM guests may switch freely between 64-bit and other modes. This in particular means that they may set registers used to pass 32-bit-mode hypercall arguments to values outside of the range 32-bit code would be able to set them to. When processing of hypercalls takes a considerable amount of time, the hypervisor may choose to invoke a hypercall continuation. Doing so involves putting (perhaps updated) hypercall arguments in respective registers. For guests not running in 64-bit mode this further involves a certain amount of translation of the values. Unfortunately internal sanity checking of these translated values assumes high halves of registers to always be clear when invoking a hypercall. When this is found not to be the case, it triggers a consistency check in the hypervisor and causes a crash.

• CWE-843Access of Resource Using Incompatible TypeThe product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.