CVE-2026-79609 — x86: XPTI may break on huge-memory systems

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
Xen / Xen	unknown consult Xen advisory XSA-516

CWE

No CWE identifiers supplied.

References

https://xenbits.xenproject.org/xsa/advisory-516.html

ADP enrichment

CVE

No English description supplied.

http://xenbits.xen.org/xsa/advisory-516.html

CISA-ADP

No English description supplied.

No references supplied.