CVE-2026-79609— x86: XPTI may break on huge-memory systems
Quick assessment
Affected
Xen Xen
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
XPTI（Xen 页表隔离）旨在缓解 Meltdown 漏洞（CVE-2017-5754，XSA-254 的一个方面）。其实现机制是将 64 位半虚拟化（PV）客户机页表项从由客户机选择的根页表复制到一个由 Xen 选定、且实际被硬件使用的根页表中。为了读取客户机的根页表，系统使用直接映射（directmap）。然而，PV 客户机的直接映射可能无法覆盖全部内存；特别是当任何内存区域超出 5 TiB（在配置了 CONFIG_BIGMEM=y 时则为 3.5 TiB）地址边界时，就会出现这种情况。
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I. Basic Information for CVE-2026-79609
Vulnerability Information
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Vulnerability Title
x86: XPTI may break on huge-memory systems
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-79609
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Advisories for CVE-2026-79609 (1)
Same Patch Batch · Xen · 2026-10-13 · 8 CVEs total
| CVE-2026-102699 | Arm: multiple issues with GNTTABOP_cache_flush | |
| CVE-2026-102700 | gnttab: cache-flush handling may cause page reference leak | |
| CVE-2026-102702 | Arm: multiple issues with GNTTABOP_cache_flush | |
| CVE-2026-79607 | Xenstore: Guests can crash xenstored during Live Update | |
| CVE-2026-79611 | VMX: VMentry failure with branch tracing and blocked states | |
| CVE-2026-79610 | grant-table: double version change race | |
| CVE-2026-79608 | x86/AMD: ineffectual Zenbleed workaround |
IV. Related Vulnerabilities
Same product: Xen
-
CVE-2026-102700
gnttab: cache-flush handling may cause page reference leak -
CVE-2026-102702
Arm: multiple issues with GNTTABOP_cache_flush -
CVE-2026-102699
Arm: multiple issues with GNTTABOP_cache_flush -
CVE-2026-79611
VMX: VMentry failure with branch tracing and blocked states -
CVE-2026-79610
grant-table: double version change race
Same vendor: Xen
-
CVE-2026-102700
gnttab: cache-flush handling may cause page reference leak -
CVE-2026-102699
Arm: multiple issues with GNTTABOP_cache_flush -
CVE-2026-102702
Arm: multiple issues with GNTTABOP_cache_flush -
CVE-2026-79611
VMX: VMentry failure with branch tracing and blocked states -
CVE-2026-79610
grant-table: double version change race
V. Comments for CVE-2026-79609
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