CVE-2026-23553

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine without logging in. Limited direct impact.

Exploit odds

0.1% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-01-28 16:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:21 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.1% in the next 30 days (EPSS).
• Severity: 2.9 LOW (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-01-28 16:16 UTC

Last modified

2026-06-17 10:21 UTC

Exploit probability

0.1% · EPSS, next 30 days

Weakness

CWE-665

Record status

Analyzed

Affected

• Xen

Attack profile CVSS 3.1 · 2.9

Attack vector

Local

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-23553.md and follow it. Check whether this project is affected by CVE-2026-23553. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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