CVE-2023-46842
Published: 16 May 2024
Summary
CVE-2023-46842 is a medium-severity Type Confusion (CWE-843) vulnerability in Fedoraproject Fedora. Its CVSS base score is 6.5 (Medium).
Operationally, ranked in the top 15.6% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
Deeper analysis
The vulnerability is a denial-of-service issue in the Xen hypervisor (XSA-454) affecting HVM guests. Unlike 32-bit PV guests, HVM guests can freely switch between 64-bit and other modes and therefore place out-of-range values in registers used to pass 32-bit hypercall arguments. When a long-running hypercall triggers a continuation, the hypervisor performs internal sanity checks on translated register values that incorrectly assume the high halves are always clear; violation of this assumption causes a hypervisor consistency check and crash.
A local attacker with a running HVM guest can exploit the flaw by arranging for a time-consuming hypercall while registers contain unexpected high-half values. Successful exploitation results in a hypervisor crash, producing a host-wide availability impact (CVSS 6.5) without requiring elevated privileges inside the guest or user interaction.
Advisories published by the Xen Project (XSA-454) and downstream distributions such as Fedora describe the issue and point to updated hypervisor packages that correct the register-value handling during hypercall continuation.
EPSS for the CVE rose from a low baseline to a peak of 0.0731 on 2025-12-11 before receding, indicating measurable post-disclosure exploitation interest.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-51008
Vulnerability details
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…
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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(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.