# CVE-2026-79609: xen: XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown (CVE-2017-5754, one aspect of XSA-254)

CVE-2026-79609 is fixed in xen on 1 platform, first by DEBIAN-CVE-2026-79609, released October 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-79609
- Priority: High
- CVSS: 8.8 (high)
- EPSS: 0.0011
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 13, 2026

## Description

XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown (CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV guest page table entries from guest-chosen root page tables to the Xen- chosen one which is in actual use by hardware.  To read the guest root page table, the directmap is used.  PV guests, however, have a directmap which may not cover all memory; in particular this is the case if any memory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address boundary.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | xen Debian 12.15 (bookworm) | 4.17.7+13-g2445b30a44-0+deb12u1 | [DEBIAN-CVE-2026-79609](https://patchblox.com/security/data/fix/linux/debian-cve-2026-79609.md) | Oct 19, 2026 |
| Linux | xen Debian 13.5 (trixie) | 4.20.4+39-gf1e1321c87-0+deb13u1 | [DEBIAN-CVE-2026-79609](https://patchblox.com/security/data/fix/linux/debian-cve-2026-79609.md) | Oct 19, 2026 |
| Linux | xen Debian 14 | 4.20.4+39-gf1e1321c87-1 | [DEBIAN-CVE-2026-79609](https://patchblox.com/security/data/fix/linux/debian-cve-2026-79609.md) | Oct 19, 2026 |
| Linux | xen sles 15.7 | 4.20.4_06-150700.3.49.2 | [SUSE-SU-2026:4942-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4942-1.md) | Nov 7, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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