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NVD / CVE Program· CNA XEN

CVE-2026-79603: Unconditionally do TLB flushing ahead of page scrubbing

MediumCVSS 4.3 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 17/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.22% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: xen (Alpine:v3.21) 4.19.6-r1; xen (Alpine:v3.22) 4.20.4-r1; xen (Alpine:v3.24) 4.21.2-r1.

Low priority for now. Upgrade to xen (Alpine:v3.21) 4.19.6-r1; xen (Alpine:v3.22) 4.20.4-r1; xen (Alpine:v3.24) 4.21.2-r1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

Published
Sep 8, 2026
Updated
Sep 8, 2026
EPSS
0.2% · 12th percentile

Report tools

JSON

Action score

17

Monitor

Low priority for now.

CVSS
17 / 40 · 4.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-79603

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (XEN). Independent of NVD's CPE analysis and usually ahead of it.

  • Xen Xen

    • consult Xen advisory XSA-511unknown

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.21xenbefore 4.19.6-r14.19.6-r1
Alpine:v3.22xenbefore 4.20.4-r14.20.4-r1
Alpine:v3.24xenbefore 4.21.2-r14.21.2-r1
Debian:12xenbefore 4.17.7+13-g2445b30a44-0+deb12u14.17.7+13-g2445b30a44-0+deb12u1
Debian:13xenbefore 4.20.4+39-gf1e1321c87-0+deb13u14.20.4+39-gf1e1321c87-0+deb13u1
Debian:14xenbefore 4.20.4+39-gf1e1321c87-14.20.4+39-gf1e1321c87-1
openSUSE:Tumbleweedxenbefore 4.22.0_04-1.14.22.0_04-1.1
SUSE:Linux Enterprise Micro 5.3xenbefore 4.16.7_14-150400.4.92.14.16.7_14-150400.4.92.1
SUSE:Linux Enterprise Micro 5.5xenbefore 4.17.6_16-150500.3.79.14.17.6_16-150500.3.79.1
SUSE:Linux Enterprise Module for Basesystem 15 SP7xenbefore 4.20.4_04-150700.3.46.14.20.4_04-150700.3.46.1
SUSE:Linux Enterprise Server 15 SP6-LTSSxenbefore 4.18.6_03-150600.3.56.14.18.6_03-150600.3.56.1

Same product

xen: all records

Other highest-scoring records for the same primary product.

  • CVE-2017-10921The grant-table feature in Xen through 4.8.x does not ensure sufficient type counts for a GNTMAP_device_map and GNTMAP_host_map mapping…
    41Plan
  • CVE-2017-10920The grant-table feature in Xen through 4.8.x mishandles a GNTMAP_device_map and GNTMAP_host_map mapping, when followed by only a…
    41Plan
  • CVE-2017-10918Xen through 4.8.x does not validate memory allocations during certain P2M operations, which allows guest OS users to obtain privileged host…
    41Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-62437Sep 8, 2026 · x86: DMs may cause mem leak by IRQ binding
    26Monitor
  • ← EarlierCVE-2026-79602Sep 8, 2026 · x86: improper handling of HVM emulation return codes
    35Monitor
  • Later →CVE-2026-102699Oct 13, 2026 · Arm: multiple issues with GNTTABOP_cache_flush
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:xen4.19.6-r1 · Alpine:v3.21Package registry (OSV)
debian:xen4.17.7+13-g2445b30a44-0+deb12u1 · Debian:12Package registry (OSV)
debian:xen4.20.4+39-gf1e1321c87-0+deb13u1 · Debian:13Package registry (OSV)
opensuse:xen4.22.0_04-1.1 · openSUSE:TumbleweedPackage registry (OSV)
suse:xen4.17.6_16-150500.3.79.1 · SUSE:Linux Enterprise Micro 5.5Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-664 · Improper Control of a Resource Through its Lifetime

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records