Skip to content
Noroxi
NVD / CVE Program· CNA XEN

CVE-2021-28705: issues with partially successful P2M updates on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/v

Noroxi assessment

Priority: Monitor (action score 31/100)

  • 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: 0.36% (FIRST EPSS).
  • Someone with local access to the system 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:v3.11) 4.13.4-r2; xen (Alpine:v3.13) 4.14.3-r2; xen (Alpine:v3.14) 4.15.1-r2.

Low priority for now. Upgrade to xen (Alpine:v3.11) 4.13.4-r2; xen (Alpine:v3.13) 4.14.3-r2; xen (Alpine:v3.14) 4.15.1-r2 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

issues with partially successful P2M updates on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] x86 HVM and PVH guests may be started in populate-on-demand (PoD) mode, to provide a way for them to later easily have more memory assigned. Guests are permitted to control certain P2M aspects of individual pages via hypercalls. These hypercalls may act on ranges of pages specified via page orders (resulting in a power-of-2 number of pages). In some cases the hypervisor carries out the requests by splitting them into smaller chunks. Error handling in certain PoD cases has been insufficient in that in particular partial success of some operations was not properly accounted for. There are two code paths affected - page removal (CVE-2021-28705) and insertion of new pages (CVE-2021-28709). (We provide one patch which combines the fix to both issues.)

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Nov 23, 2021
Updated
Jun 16, 2026
EPSS
0.3% · 28th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

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-2021-28705

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

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for xen records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

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.

We use this product, ask for help

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.

VendorProduct
xenxen
fedoraprojectfedora
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux11.0
  • fedoraproject fedora34
  • fedoraproject fedora35
  • xen xen3.4.0 and later · up to 4.12.4 inclusive
  • xen xen4.13.0 and later · up to 4.13.4 inclusive
  • xen xen4.14.0 and later · up to 4.14.3 inclusive
  • xen xen4.15.0
  • xen xen4.15.1

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

    • 4.14.x, 4.12.x, 4.15.x, xen-unstable, 4.13.xaffected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Alpine:v3.11xenfrom 3.4.0 · before 4.13.4-r24.13.4-r2
Alpine:v3.13xenfrom 3.4.0 · before 4.14.3-r24.14.3-r2
Alpine:v3.14xenfrom 3.4.0 · before 4.15.1-r24.15.1-r2
Debian:11xenbefore 4.14.3+32-g9de3671772-1~deb11u14.14.3+32-g9de3671772-1~deb11u1
Debian:12xenbefore 4.14.3+32-g9de3671772-14.14.3+32-g9de3671772-1
openSUSE:Leap 15.2xenbefore 4.13.4_02-lp152.2.33.14.13.4_02-lp152.2.33.1
openSUSE:Leap 15.3xenbefore 4.14.3_04-3.15.14.14.3_04-3.15.1
SUSE:HPE Helion OpenStack 8xenbefore 4.9.4_24-3.97.14.9.4_24-3.97.1
SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOSxenbefore 4.12.4_16-3.57.14.12.4_16-3.57.1
SUSE:Linux Enterprise High Performance Computing 15-ESPOSxenbefore 4.10.4_30-3.68.14.10.4_30-3.68.1
SUSE:Linux Enterprise Module for Basesystem 15 SP2xenbefore 4.13.4_02-3.40.14.13.4_02-3.40.1
SUSE:Linux Enterprise Module for Basesystem 15 SP3xenbefore 4.14.3_04-3.15.14.14.3_04-3.15.1
SUSE:Linux Enterprise Server 11 SP4-LTSSxenbefore 4.4.4_50-61.67.14.4.4_50-61.67.1
SUSE:Linux Enterprise Server 12 SP2-BCLxenbefore 4.7.6_18-43.82.14.7.6_18-43.82.1
SUSE:Linux Enterprise Software Development Kit 12 SP5xenbefore 4.12.4_16-3.55.14.12.4_16-3.55.1
SUSE:OpenStack Cloud 9xenbefore 4.11.4_24-2.65.14.11.4_24-2.65.1

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, whi
    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 GNTMAP_host
    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-2021-28707Nov 23, 2021 · PoD operations on misaligned GFNs T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities cor
    35Monitor
  • ← EarlierCVE-2021-28708Nov 23, 2021 · PoD operations on misaligned GFNs T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities cor
    35Monitor
  • Later →CVE-2021-28709Nov 23, 2021 · issues with partially successful P2M updates on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/v
    31Monitor

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:xen4.13.4-r2 · Alpine:v3.11Package registry (OSV)
debian:xen4.14.3+32-g9de3671772-1 · Debian:12Package registry (OSV)
opensuse:xen4.13.4_02-lp152.2.33.1 · openSUSE:Leap 15.2Package registry (OSV)
suse:xen4.4.4_50-61.67.1 · SUSE:Linux Enterprise Server 11 SP4-LTSSPackage 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

  • Someone with local access to the system 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
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-755 · Improper Handling of Exceptional Conditions

CVSS vector

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

nvd-primary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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

References

Show all references (4 more)

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

All records