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CVE-2026-79603

Unconditionally do TLB flushing ahead of page scrubbing

4.3 MediumFix available

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.22%Unchanged since Sep 9, 2026
90%50%10%1%

What each source reports

CVE List Score used 4.3

Unconditionally do TLB flushing ahead of page scrubbing

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
CVE-2026-79603
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-664
Updated
2026-11-02
EUVDEUVD-2026-72721 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
EUVD-2026-72721
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-pwv5-r8hr-fvgr 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A...

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
GHSA-pwv5-r8hr-fvgr
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-664
Updated
2026-11-02
NVD 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
CVE-2026-79603
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-664
Updated
2026-11-02
OSVALPINE-CVE-2026-79603 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
ALPINE-CVE-2026-79603
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2026-79603 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
DEBIAN-CVE-2026-79603
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-04
Show 5 moreShow less
OSVUBUNTU-CVE-2026-79603 4.3

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Record
UBUNTU-CVE-2026-79603
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVopenSUSE-SU-2026:11738-1 No score

xen-4.22.0_04-1.1 on GA media

These are all security issues fixed in the xen-4.22.0_04-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11738-1
Updated
2026-11-02
OSVSUSE-SU-2026:4087-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2026-62437: x86: DMs may cause mem leak by IRQ binding (bsc#1276838).
  • CVE-2026-79602: x86: improper handling of HVM emulation return codes (bsc#1276839).
  • CVE-2026-79603: unconditionally do TLB flushing ahead of page scrubbing (bsc#1276841).
Record
SUSE-SU-2026:4087-1
Updated
2026-11-02
OSVSUSE-SU-2026:4088-1 No score

Security update for xen

This update for xen fixes the following issues:

  • CVE-2026-62437: x86: DMs may cause mem leak by IRQ binding (bsc#1276838).
  • CVE-2026-79602: x86: improper handling of HVM emulation return codes (bsc#1276839).
  • CVE-2026-79603: unconditionally do TLB flushing ahead of page scrubbing (bsc#1276841).
Record
SUSE-SU-2026:4088-1
Updated
2026-11-02
OSVSUSE-SU-2026:4090-1 No score

Security update for xen

This update for xen fixes the following issues:

Update to version 4.20.3 (jsc#PED-8907).

Security issues fixed:

  • CVE-2026-42493: x86 shadow paging is deprecated (bsc#1271528).
  • CVE-2026-42494,CVE-2026-42495,CVE-2026-62423,CVE-2026-62424,CVE-2026-62425: buffer overruns in libfsimage iso9660 handling (bsc#1271530).
  • CVE-2026-62426,CVE-2026-62427: sysctl and platform-op locks open to abuse (bsc#1271531).
  • CVE-2026-62428: grant-table: type confusion in grant-copy (bsc#1271532).
  • CVE-2026-62429: vNUMA domain cleanup may race other operations (bsc#1271534).
  • CVE-2026-62430: x86: Out-of-bounds read in vRTC emulation (bsc#1271535).
  • CVE-2026-62431: Viridian STIMER division by zero (bsc#1271536).
  • CVE-2026-62432: evtchn: Race between FIFO expand and reset (bsc#1271537).
  • CVE-2026-62433: correct buffer checks for DM_OP hypercalls (bsc#1271538).
  • CVE-2026-62434: PoD: Don't try to reclaim special pages (bsc#1271539).
  • CVE-2026-62437: x86: DMs may cause mem leak by IRQ binding (bsc#1276838).
  • CVE-2026-79602: x86: improper handling of HVM emulation return codes (bsc#1276839).
  • CVE-2026-79603: unconditionally do TLB flushing ahead of page scrubbing (bsc#1276841).
  • pygrub is only supported in de-privileged mode (bsc#1271947).

Non security issue fixed:

  • Xen: Missing upstream bug fixes (bsc#1027519).
Record
SUSE-SU-2026:4090-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
xen
Alpine:v3.21
 before 4.19.6-r1
4.19.6-r1
xen
Alpine:v3.22
 before 4.20.4-r1
4.20.4-r1
xen
Alpine:v3.23
 before 4.20.4-r1
4.20.4-r1
xen
Alpine:v3.24
 before 4.21.2-r1
4.21.2-r1
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 4.17.6_16-150500.3.79.1
4.17.6_16-150500.3.79.1
xen
SUSE:Linux Enterprise Micro 5.3
 before 4.16.7_14-150400.4.92.1
4.16.7_14-150400.4.92.1
xen
SUSE:Linux Enterprise Micro 5.4
 before 4.16.7_14-150400.4.92.1
4.16.7_14-150400.4.92.1
Show 10 moreShow less
Affected packages
PackageAffectedFixed
xen
SUSE:Linux Enterprise Module for Basesystem 15 SP7
 before 4.20.4_04-150700.3.46.1
4.20.4_04-150700.3.46.1
xen
SUSE:Linux Enterprise Module for Server Applications 15 SP7
 before 4.20.4_04-150700.3.46.1
4.20.4_04-150700.3.46.1
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_04-1.1
4.22.0_04-1.1

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-2026-79603 is a medium vulnerability (CVSS 4.3) in Xen, published September 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. Fixed in xen 4.19.6-r1.

References

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