Vulnerability Database

322,129

Total vulnerabilities in the database

CVE-2026-23553

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.

  • Published: Jan 28, 2026
  • Updated: Jan 29, 2026
  • CVE: CVE-2026-23553
  • Severity: Low
  • Exploit:

CVSS v3:

  • Severity: Low
  • Score: 2.9
  • AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CWEs:

Software From Fixed in
xen / xen 4.6.0 4.6.0.x