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CVE-2026-79609

x86: XPTI may break on huge-memory systems

8.8 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.11%Down 0.1 points since Oct 14, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.8

x86: XPTI may break on huge-memory systems

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.

Record
CVE-2026-79609
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-284
Updated
2026-11-02
EUVDEUVD-2026-98825 8.8

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.

Record
EUVD-2026-98825
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-842c-7fjj-j8jj 8.8

XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown (CVE-2017-5754, one aspect of...

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.

Record
GHSA-842c-7fjj-j8jj
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-284
Updated
2026-11-02
NVD 8.8

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.

Record
CVE-2026-79609
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weakness
CWE-284
Updated
2026-11-02
OSVALPINE-CVE-2026-79609 8.8

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.

Record
ALPINE-CVE-2026-79609
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2026-79609 8.8

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.

Record
DEBIAN-CVE-2026-79609
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-04
Show 6 moreShow less
OSVUBUNTU-CVE-2026-79609 8.8

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.

Record
UBUNTU-CVE-2026-79609
CVSS 3.1
8.8 HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2026:12138-1 No score

xen-4.22.0_06-1.1 on GA media

These are all security issues fixed in the xen-4.22.0_06-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:12138-1
Updated
2026-11-02
OSVSUSE-SU-2026:4641-1 No score

Security update for xen

This update for xen fixes the following issues:

Security issues fixed:

  • CVE-2026-79609: x86: XPTI may break on huge-memory systems (bsc#1283321).
  • CVE-2026-79610: grant-table: double version change race (bsc#1283322).
  • CVE-2026-79611: VMX: VMentry failure with branch tracing and blocked states (bsc#1283323).
  • CVE-2026-102700: gnttab: cache-flush handling may cause page reference leak (bsc#1283325).

Non security issue fixed:

  • Xen: Missing upstream bug fixes (bsc#1027519).
Record
SUSE-SU-2026:4641-1
Updated
2026-11-02
OSVSUSE-SU-2026:4642-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2026-79609: x86: XPTI may break on huge-memory systems (bsc#1283321).
  • CVE-2026-79610: grant-table: double version change race (bsc#1283322).
  • CVE-2026-79611: VMX: VMentry failure with branch tracing and blocked states (bsc#1283323).
  • CVE-2026-102700: gnttab: cache-flush handling may cause page reference leak (bsc#1283325).
Record
SUSE-SU-2026:4642-1
Updated
2026-11-02
OSVSUSE-SU-2026:4732-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2026-79609: x86: XPTI may break on huge-memory systems (bsc#1283321).
  • CVE-2026-79610: grant-table: double version change race (bsc#1283322).
  • CVE-2026-79611: VMX: VMentry failure with branch tracing and blocked states (bsc#1283323).
  • CVE-2026-102700: gnttab: cache-flush handling may cause page reference leak (bsc#1283325).
Record
SUSE-SU-2026:4732-1
Updated
2026-11-02
OSVSUSE-SU-2026:4942-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2026-79608: x86/AMD: ineffectual Zenbleed workaround (bsc#1283317).
  • CVE-2026-79609: x86: XPTI may break on huge-memory systems (bsc#1283321).
  • CVE-2026-79610: grant-table: double version change race (bsc#1283322).
  • CVE-2026-79611: VMX: VMentry failure with branch tracing and blocked states (bsc#1283323).
  • CVE-2026-102700: gnttab: cache-flush handling may cause page reference leak (bsc#1283325).
Record
SUSE-SU-2026:4942-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
xen
Alpine:v3.21
 before 4.19.6-r2
4.19.6-r2
xen
Alpine:v3.22
 before 4.20.4-r2
4.20.4-r2
xen
Alpine:v3.23
 before 4.20.4-r2
4.20.4-r2
xen
Alpine:v3.24
 before 4.21.2-r2
4.21.2-r2
xen
Debian:12
 before 4.17.7+13-g2445b30a44-0+deb12u1, plus listed versions
4.17.1+2-gb773c48e36-14.17.2+55-g0b56bed864-14.17.2+76-ge1f9cb16e2-14.17.2+76-ge1f9cb16e2-1~deb12u14.17.2-1
Show 10 moreShow less
4.17.3+10-g091466ba55-14.17.3+10-g091466ba55-1.14.17.3+10-g091466ba55-1.1~exp14.17.3+10-g091466ba55-1.1~exp24.17.3+10-g091466ba55-1~deb12u14.17.3+36-g54dacb5c02-14.17.5+23-ga4e5191dc0-14.17.5+23-ga4e5191dc0-1+deb12u14.17.5+72-g01140da4e8-14.17.7-0+deb12u1
4.17.7+13-g2445b30a44-0+deb12u1
xen
Debian:13
 before 4.20.4+39-gf1e1321c87-0+deb13u1, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+37-g61ff35323e-0+deb13u14.20.2+37-g61ff35323e-14.20.2+7-g1badcf5035-0+deb13u14.20.2+7-g1badcf5035-14.20.2+7-g1badcf5035-24.20.3+127-gc42374a105-0+deb13u14.20.3+127-gc42374a105-1
4.20.4+39-gf1e1321c87-0+deb13u1
xen
Debian:14
 before 4.20.4+39-gf1e1321c87-1, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+37-g61ff35323e-14.20.2+7-g1badcf5035-14.20.2+7-g1badcf5035-24.20.3+127-gc42374a105-1
4.20.4+39-gf1e1321c87-1
xen
SUSE:Linux Enterprise Micro 5.5
 before 4.17.7_02-150500.3.82.1
4.17.7_02-150500.3.82.1
xen
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS
 before 4.17.7_02-150500.3.82.1
4.17.7_02-150500.3.82.1
xen
SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS
 before 4.17.7_02-150500.3.82.1
4.17.7_02-150500.3.82.1
Show 20 moreShow less
Affected packages
PackageAffectedFixed
xen
SUSE:Linux Enterprise Server 15 SP5-LTSS
 before 4.17.7_02-150500.3.82.1
4.17.7_02-150500.3.82.1
xen
SUSE:Linux Enterprise Server for SAP Applications 15 SP5
 before 4.17.7_02-150500.3.82.1
4.17.7_02-150500.3.82.1
xen
SUSE:Linux Enterprise Micro 5.3
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise Micro 5.4
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise Server 15 SP4-LTSS
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise Server for SAP Applications 15 SP4
 before 4.16.7_16-150400.4.95.1
4.16.7_16-150400.4.95.1
xen
SUSE:Linux Enterprise Server 12 SP5-LTSS
 before 4.12.4_76-3.154.1
4.12.4_76-3.154.1
xen
SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5
 before 4.12.4_76-3.154.1
4.12.4_76-3.154.1
xen
SUSE:Linux Enterprise Module for Basesystem 15 SP7
 before 4.20.4_06-150700.3.49.2
4.20.4_06-150700.3.49.2
xen
SUSE:Linux Enterprise Module for Server Applications 15 SP7
 before 4.20.4_06-150700.3.49.2
4.20.4_06-150700.3.49.2
xen
Ubuntu:16.04:LTS
 All versions, plus listed versions
4.5.1-0ubuntu14.5.1-0ubuntu24.6.0-1ubuntu14.6.0-1ubuntu24.6.0-1ubuntu4
Show 7 moreShow less
4.6.0-1ubuntu4.14.6.0-1ubuntu4.24.6.0-1ubuntu4.34.6.5-0ubuntu14.6.5-0ubuntu1.14.6.5-0ubuntu1.24.6.5-0ubuntu1.4
 None known
xen
Ubuntu:18.04:LTS
 All versions, plus listed versions
4.9.0-0ubuntu34.9.0-0ubuntu44.9.2-0ubuntu1
 None known
xen
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.9.2-0ubuntu24.9.2-0ubuntu64.9.2-0ubuntu74.11.3+24-g14b62ab3e5-1ubuntu14.11.3+24-g14b62ab3e5-1ubuntu24.11.3+24-g14b62ab3e5-1ubuntu2.24.11.3+24-g14b62ab3e5-1ubuntu2.3
 None known
xen
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.11.4+24-gddaaccbbab-1ubuntu24.16.0-1~ubuntu24.16.0-1~ubuntu2.1
 None known
xen
Ubuntu:24.04:LTS
 All versions, plus listed versions
4.17.2-14.17.2+55-g0b56bed864-14.17.2+76-ge1f9cb16e2-14.17.2+76-ge1f9cb16e2-1ubuntu14.17.3+10-g091466ba55-14.17.3+10-g091466ba55-1.1ubuntu24.17.3+10-g091466ba55-1.1ubuntu3
 None known
xen
Ubuntu:26.10
 All versions, plus listed versions
4.20.2+7-g1badcf5035-2build24.20.2+37-g61ff35323e-1ubuntu14.20.3+127-gc42374a105-1
 None known
xen
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.20.0+68-g35cb38b222-14.20.2+7-g1badcf5035-24.20.2+7-g1badcf5035-2build2
 None known
xen
openSUSE:Tumbleweed
 before 4.22.0_06-1.1
4.22.0_06-1.1

History

History
RecordedChangedSources
affected, factsOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-79609 is a high vulnerability (CVSS 8.8) in Xen, published October 13, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.11%, the 1st percentile. Fixed in xen 4.19.6-r2.

References

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