🛡️ CVE-2026-23553
🟢 CVSS 2.9 — Low ✅ No Known Exploit CWE-665 NVD
2.9
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Details

Severity LOW
CVSS Score 2.9
CVSS Vector CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE CWE-665
Public Exploit ✅ No
Source NVD
Published 2026-01-28
Updated 2026-06-02
Modified 2026-02-09

Affected Packages

Software From version Fixed in
xen 4.6.0 —

References

Mitigation, Patch, Vendor Advisory https://xenbits.xenproject.org/xsa/advisory-479.html
Mailing List, Mitigation, Patch, Third Party Advisory http://www.openwall.com/lists/oss-security/2026/01/27/3
Mitigation, Patch, Vendor Advisory http://xenbits.xen.org/xsa/advisory-479.html

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