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

What is CVE-2023-46842?

CVE-2023-46842 is a medium-severity denial of service vulnerability in Fedoraproject Fedora, published on 16 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.

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.

Weakness: CWE-843

Which versions are affected by CVE-2023-46842?

It affects 2 products.

Products include Fedoraproject Fedora, Xen Xen.

How do I fix CVE-2023-46842?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-46842 being exploited?

There is no known exploitation of CVE-2023-46842 in the wild and no public exploit code.

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Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2023-46842, DEBIAN-CVE-2023-46842, GHSA-hcr5-hp8w-36q9, UBUNTU-CVE-2023-46842.