CVE-2026-23553

Intra-guest information disclosure via skipped IBPB

Published Jan 28, 2026 · Updated Jan 28, 2026

Information disclosure in Xen 4.6 and newer allows local users in a guest to obtain information intended to be private in that guest. The x86 context-switch logic skips an indirect branch prediction barrier when a vCPU returns to its previous physical CPU, leaving the prior task's branch-target-buffer training in place. Exploitation requires x86 hardware, vCPU migration between physical CPUs, and a guest task switch; default IBPB-on-entry settings on SRSO-affected systems prevent exposure.

CVSS severity2.9
Low
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Xen 4.6 and newer allows local users in a guest to obtain information intended to be private in that guest. The x86 context-switch logic skips an indirect branch prediction barrier when a vCPU returns to its previous physical CPU, leaving the prior task's branch-target-buffer training in place. Exploitation requires x86 hardware, vCPU migration between physical CPUs, and a guest task switch; default IBPB-on-entry settings on SRSO-affected systems prevent exposure.

The record

CVE
CVE-2026-23553
Published
Jan 28, 2026
Updated
Jan 28, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-665, CWE-693, T1005
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

2.9CISA-ADPCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-665Improper Initialization
CWE-693Protection Mechanism Failure
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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