VULNERABILITY INTELLIGENCE

CVE-2026-23553

CVSS score2.9 LOW
EPSS probability0.14%
CISA KEVNot currently listed
Published2026-01-28
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

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.

Weakness classification

  • 134c704f-9b21-4f2e-91b3-4a467353bcc0: CWE-665

Primary references