CVE-2026-23553

LOW EPSS 2.9%
Published Jan 28, 20265mo ago · Modified Jun 17, 20262w ago
2.9 CVSS 3.1
Low
Find Similar
Published Jan 28, 2026 5mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
2.9
Exploitability
1.4
Impact
1.4
Vector string
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Attack Vector Local
Attack Complexity High
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity None
Availability None

Threat Intelligence

EPSS Exploit Probability
2.9% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 2

CWE-665
CWE-693

Affected Products 1

VendorProductVersionRange
xenxen*≥4.6.0

References 3

  • openwall.com http://www.openwall.com/lists/oss-security/2026/01/27/3
    Mailing ListMitigationPatchThird Party Advisory
  • xenbits.xen.org http://xenbits.xen.org/xsa/advisory-479.html
    MitigationPatchVendor Advisory
  • xenbits.xenproject.org https://xenbits.xenproject.org/xsa/advisory-479.html
    MitigationPatchVendor Advisory

Remediation

  • openwall.com http://www.openwall.com/lists/oss-security/2026/01/27/3
    Mailing ListMitigationPatchThird Party Advisory
  • xenbits.xen.org http://xenbits.xen.org/xsa/advisory-479.html
    MitigationPatchVendor Advisory
  • xenbits.xenproject.org https://xenbits.xenproject.org/xsa/advisory-479.html
    MitigationPatchVendor Advisory