CVE-2026-79609

Name	CVE-2026-79609
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 (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DSA-6571-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xen (PTS)	bookworm	4.17.5+72-g01140da4e8-1	vulnerable
	bookworm (security)	4.17.7-0+deb12u1	vulnerable
	trixie	4.20.3+127-gc42374a105-0+deb13u1	vulnerable
	trixie (security)	4.20.4+39-gf1e1321c87-0+deb13u1	fixed
	forky	4.20.3+127-gc42374a105-1	vulnerable
	sid	4.20.4+39-gf1e1321c87-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
xen	source	trixie	4.20.4+39-gf1e1321c87-0+deb13u1		DSA-6571-1
xen	source	(unstable)	4.20.4+39-gf1e1321c87-1

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