CVE-2026-23553
x86: incomplete IBPB for vCPU isolation
Vexday Risk Score
8Baixo
Decisão SSVC (CISA)
Track
Sem sinal de exploração → monitorar
CVSS 2.9EPSS 0.1%KEV nãoPoC —Nuclei —Metasploit —Patch —
Ciclo de vida
28 jan 2026Publicada no NVD
Recomendação: Monitorar — sem sinal de exploração no momento.
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:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Produtos afetados
Xen · XenQuer saber se a sua infraestrutura está exposta a isto?
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