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Xen: Use after free of paging structures in EPT (XSA-480)

high Nessus Plugin ID 318807

Synopsis

The remote Xen hypervisor installation is missing a security update.

Description

The Intel EPT paging code uses an optimization to defer flushing of any cached EPT state until the p2m lock is dropped, so that multiple modifications done under the same locked region only issue a single flush. Freeing of paging structures however is not deferred until the flushing is done, and can result in freed pages transiently being present in cached state. Such stale entries can point to memory ranges not owned by the guest, thus allowing access to unintended memory regions.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Apply the appropriate patch according to the vendor advisory.

See Also

https://xenbits.xenproject.org/xsa/advisory-480.html

Plugin Details

Severity: High

ID: 318807

File Name: xen_server_XSA-480.nasl

Version: 1.1

Type: Local

Family: Misc.

Published: 6/5/2026

Updated: 6/5/2026

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.3

CVSS v2

Risk Factor: Medium

Base Score: 6

Vector: CVSS2#AV:L/AC:H/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-23554

CVSS v3

Risk Factor: High

Base Score: 7.8

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Vulnerability Information

CPE: cpe:/o:xen:xen

Required KB Items: installed_sw/Xen Hypervisor, Settings/ParanoidReport

Patch Publication Date: 3/17/2026

Vulnerability Publication Date: 3/17/2026

Reference Information

CVE: CVE-2026-23554

IAVB: 2026-B-0069