How severe is CVE-2026-23553?

CVE-2026-23553 has a CVSS 3.x base score of 2.9, rated low severity. It is exploitable over local access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2026-23553 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23553?

CVE-2026-23553 affects Xen. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23553?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-23553 have an EU (EUVD) identifier?

Yes. CVE-2026-23553 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4882.

When was CVE-2026-23553 published?

CVE-2026-23553 was published on 2026-01-28 and last updated on 2026-06-17.

CVE-2026-23553

CVE-2026-23553 is a low-severity vulnerability in Xen with a CVSS 3.x base score of 2.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-665.

Key facts

Severity: Low (CVSS 3.x base score 2.9)
EPSS exploit prediction: 0% (3rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-4882
Weakness: CWE-665
Affected product: Xen
Published: 2026-01-28
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-23553?: CVE-2026-23553 has a CVSS 3.x base score of 2.9, rated low severity. It is exploitable over local access with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2026-23553 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (3rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23553?: CVE-2026-23553 affects Xen. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23553?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-23553 have an EU (EUVD) identifier?: Yes. CVE-2026-23553 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4882.
When was CVE-2026-23553 published?: CVE-2026-23553 was published on 2026-01-28 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:xen:xen:*:*:*:*:*:*:x86:*

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