CVE-2026-42487: x86 HVM I/O port list traversal

Severity: high (CVSS 7.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-18 · updated 2026-06-22
Weakness: CWE-362

Description

HVM guest I/O port accesses are subject to either emulation or at least translation. Translations are managed by the device model (via XEN_DOMCTL_ioport_mapping), and hence the linked list used may changed at any time. Traversal of those lists (while handling guest I/O port accesses) therefore needs synchronizing with updates, which was missing so far.

References

https://xenbits.xenproject.org/xsa/advisory-491.html
http://www.openwall.com/lists/oss-security/2026/06/09/11
http://xenbits.xen.org/xsa/advisory-491.html

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