CVE-2026-23553

LOW

2.9

Description

In the context switch logic Xen attempts to skip an IBPB in the case of a vCPU returning to a CPU on which it was the previous vCPU to run. While safe for Xen's isolation between vCPUs, this prevents the guest kernel correctly isolating between tasks. Consider: 1) vCPU runs on CPU A, running task 1. 2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB. 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB. 4) vCPU moves back to CPU A. Xen skips IBPB again. Now, task 2 is running on CPU A with task 1's training still in the BTB.

CVE Details

CVSS v3.1 Score2.9

SeverityLOW

CVSS VectorCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack VectorLOCAL

ComplexityHIGH

Privileges RequiredNONE

User InteractionNONE

Published1/28/2026

Last Modified2/9/2026

Sourcenvd

Honeypot Sightings0

Affected Products

xen:xen

Weaknesses (CWE)

CWE-665CWE-693

References

https://xenbits.xenproject.org/xsa/advisory-479.html(security@xen.org)

http://www.openwall.com/lists/oss-security/2026/01/27/3(af854a3a-2127-422b-91ae-364da2661108)

http://xenbits.xen.org/xsa/advisory-479.html(af854a3a-2127-422b-91ae-364da2661108)

IOC Correlations

No correlations recorded

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