# CVE-2026-42492 — Xen

> As of 2026-07-28, CVE-2026-42492 is a HIGH-severity vulnerability in Xen, CVSS v3.1 7.5, EPSS 0.4% (38.7th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-42492, most recently “Multiple Vulnerabilities in Citrix XenServer 8.4 and 9 Enable Guest-to-Host Escalation and Denial of Service (CVE-2026-42492, CVE-2026-62428, CVE-2026-62431, CVE-2026-62432, CVE-2026-62434, CVE-2026-62435, CVE-2026-62436)”.

**Last updated:** 2026-07-28

## What is CVE-2026-42492?

Xenstore, to have an up-to-date picture of the entire system, wants to know of domains appearing and disappearing. To make this more robust, a new XEN_DOMCTL_get_domain_state was introduced. The management of the bitmap underlying that operation is tied into the binding of the VIRQ_DOM_EXC virtual IRQ. Unfortunately an error path there would tear down the bitmap even in cases when it wasn't set up. Unprivileged domains can trigger that error path.

The record classifies CVE-2026-42492 under weakness class [CWE-459](https://intel.threadlinqs.com/cwe/CWE-459). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 69 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.5 — HIGH (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 38.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 5.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-28

## Is CVE-2026-42492 being exploited?

No public exploitation evidence for CVE-2026-42492 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-07-28. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

## Affected products and versions

- **Xen**: Xen

## How to fix CVE-2026-42492

No vendor patch reference has been recorded for CVE-2026-42492 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-42492

1 tracked threat in the Threadlinqs corpus references CVE-2026-42492, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Multiple Vulnerabilities in Citrix XenServer 8.4 and 9 Enable Guest-to-Host Escalation and Denial of Service (CVE-2026-42492, CVE-2026-62428, CVE-2026-62431, CVE-2026-62432, CVE-2026-62434, CVE-2026-62435, CVE-2026-62436)](https://intel.threadlinqs.com/threat/TL-2026-1781) — HIGH · 2026-07-31

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-01. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [xenbits.xenproject.org](https://xenbits.xenproject.org/xsa/advisory-496.html)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-42492
Full detection coverage and IOCs for threats exploiting CVE-2026-42492 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp