CVE-2026-23558

Host-wide impact via status-page mapping race

Published May 19, 2026 · Updated May 19, 2026

Race condition in Xen 4.0 and later allows guest OS users to retain mappings to freed grant-table status pages. A v2-to-v1 grant-table transition can free status pages while XENMEM_add_to_physmap concurrently inserts their mappings into the guest's secondary P2M tables. Only x86 HVM and PVH guests permitted to use grant-table v2 interfaces can reach the race; Xen states that privilege escalation, information disclosure, and host-wide service interruption cannot be excluded.

CVSS severity7.8
High
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Xen 4.0 and later allows guest OS users to retain mappings to freed grant-table status pages. A v2-to-v1 grant-table transition can free status pages while XENMEM_add_to_physmap concurrently inserts their mappings into the guest's secondary P2M tables. Only x86 HVM and PVH guests permitted to use grant-table v2 interfaces can reach the race; Xen states that privilege escalation, information disclosure, and host-wide service interruption cannot be excluded.

The record

CVE
CVE-2026-23558
Published
May 19, 2026
Updated
May 19, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-362, T1499.004, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 19, 2026CVE publishedPublication date reported by the CVE source.
  2. May 19, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation
T1068Exploitation for Privilege Escalation

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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