CVE-2026-62430

x86: Out-of-bounds read in vRTC emulation

Published Jul 28, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
Accesses to the CMOS memory contents are done using an indirect IO port
pair. Therefore Xen needs to cache the guest chosen index, and one of
the usages of the index didn't take the necessary locking to avoid
concurrent changes. As a result, a guest could change the index after
it being checked, causing a subsequent out-of-bound read access to the
contents of an array.

Remediation

Vendor Workaround

Running only PV or PVH guests will avoid the vulnerability.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4818-1 xen security update
Debian DSA Debian DSA DSA-6424-1 xen security update
History
Type Values Removed Values Added
First Time appeared Xen
Xen xen
Vendors & Products Xen
Xen xen
Type Values Removed Values Added
Description Accesses to the CMOS memory contents are done using an indirect IO port pair. Therefore Xen needs to cache the guest chosen index, and one of the usages of the index didn't take the necessary locking to avoid concurrent changes. As a result, a guest could change the index after it being checked, causing a subsequent out-of-bound read access to the contents of an array.
Title x86: Out-of-bounds read in vRTC emulation
Weaknesses CWE-362
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
XEN
Published
Updated
Jul 28, 2026, 4:33 PM
Reserved
Jul 14, 2026, 10:28 AM
Status
Deferred
Published
Jul 28, 2026, 1:19 PM
Modified
Jul 28, 2026, 5:16 PM