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CVE-2026-42487

x86 HVM I/O port list traversal

High7.9EPSS 0.10%
Published
Updated
Reserved
Assigned by
XEN

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.

Scores

CVSS scores of CVE-2026-42487, by who scored it
Scored byCVSSScoreVector
CISA-ADPADP (enrichment)3.1High7.9CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
NVDNVD · Deferred3.1High7.9CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
EPSS (exploitation in 30 days)
0.10% · top 99% of all CVEs (6 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.9.

Weakness

Affected products

  • Xen · Xen

    • unknown consult Xen advisory XSA-491

What to do

Workaround: Running only PV or PVH guests will avoid the vulnerability. (Switching from a device model stub domain or a de-privileged device model to a fully privileged Dom0 device model does NOT mitigate this vulnerability. Rather, it simply recategorises the vulnerability to hostile management code, regarding it "as designed"; thus it merely reclassifies these issues as "not a bug". The security of a Xen system using stub domains is still better than with a qemu-dm running as a Dom0 process. Users and vendors of stub qemu dm systems should not change their configuration to use a Dom0 qemu process.)

References (3)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

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Record last updated .