CVE-2023-46842mediumCWE-843

CVE-2023-46842: medium-severity vulnerability in Xen

x86 HVM hypercalls may trigger Xen bug check

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.5epss 8.5%
In short

HVM virtual machines in Xen can crash the hypervisor by switching between processor modes and setting CPU registers to invalid values during long-running hypercalls. This causes a safety check in the hypervisor to fail, bringing down the system.

Technical detail

CWE-843 (Type Confusion) vulnerability in Xen's HVM hypercall handling where mode-switching guests can set 32-bit hypercall argument registers to 64-bit values that violate internal sanity checks during hypercall continuation, triggering a hypervisor crash via assertion failure.

Summary generated and translated by AI from the official 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.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
Affected products
Xen · Xen
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