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.
References
| Link | Resource |
|---|---|
| https://xenbits.xenproject.org/xsa/advisory-479.html | Mitigation Patch Vendor Advisory |
| http://www.openwall.com/lists/oss-security/2026/01/27/3 | Mailing List Mitigation Patch Third Party Advisory |
| http://xenbits.xen.org/xsa/advisory-479.html | Mitigation Patch Vendor Advisory |
Configurations
History
09 Feb 2026, 18:46
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://xenbits.xenproject.org/xsa/advisory-479.html - Mitigation, Patch, Vendor Advisory | |
| References | () http://www.openwall.com/lists/oss-security/2026/01/27/3 - Mailing List, Mitigation, Patch, Third Party Advisory | |
| References | () http://xenbits.xen.org/xsa/advisory-479.html - Mitigation, Patch, Vendor Advisory | |
| First Time |
Xen
Xen xen |
|
| CPE | cpe:2.3:o:xen:xen:*:*:*:*:*:*:x86:* |
28 Jan 2026, 17:16
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 2.9 |
| CWE | CWE-665 CWE-693 |
|
| References |
|
28 Jan 2026, 16:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-01-28 16:16
Updated : 2026-02-09 18:46
NVD link : CVE-2026-23553
Mitre link : CVE-2026-23553
CVE.ORG link : CVE-2026-23553
JSON object : View
Products Affected
xen
- xen