CVE-2021-28701: Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory.
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: 0.26% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: xen (Alpine:v3.11) 4.13.3-r3; xen (Alpine:v3.13) 4.14.2-r1; xen (Alpine:v3.14) 4.15.0-r3.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to xen (Alpine:v3.11) 4.13.3-r3; xen (Alpine:v3.13) 4.14.2-r1; xen (Alpine:v3.14) 4.15.0-r3 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
Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed.
- Published
- Sep 8, 2021
- Updated
- Jun 16, 2026
- EPSS
- 0.2% · 18th percentile
- CWE
- CWE-362
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
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.
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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.
We use this product, ask for helpAffected 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.
| Vendor | Product | CPE |
|---|---|---|
| xen | xen | cpe:2.3:o:xen:xen |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
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 fedora33
- fedoraproject fedora34
- fedoraproject fedora35
- xen xen4.0.0 and later
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
- 4.11.xaffected
- unspecified and later · before 4.12unknown
- 4.15.x and later · before unspecifiedaffected
- next of xen-unstable and later · before unspecifiednot affected
- unspecified and later · before 4.12unknown
- 4.12.x and later · before unspecifiedaffected
- next of 4.14.x and later · before unspecifiednot affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.11 | xen | from 4.0.0 · before 4.13.3-r3 | 4.13.3-r3 |
| Alpine:v3.13 | xen | from 4.0.0 · before 4.14.2-r1 | 4.14.2-r1 |
| Alpine:v3.14 | xen | from 4.0.0 · before 4.15.0-r3 | 4.15.0-r3 |
| Debian:11 | xen | before 4.14.3-1~deb11u1 | 4.14.3-1~deb11u1 |
| Debian:12 | xen | before 4.14.3-1 | 4.14.3-1 |
| openSUSE:Leap 15.2 | xen | before 4.13.3_04-lp152.2.30.1 | 4.13.3_04-lp152.2.30.1 |
| openSUSE:Leap 15.3 | xen | before 4.14.2_06-3.12.1 | 4.14.2_06-3.12.1 |
| SUSE:HPE Helion OpenStack 8 | xen | before 4.9.4_22-3.94.2 | 4.9.4_22-3.94.2 |
| SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOS | xen | before 4.12.4_16-3.57.1 | 4.12.4_16-3.57.1 |
| SUSE:Linux Enterprise High Performance Computing 15-ESPOS | xen | before 4.10.4_30-3.68.1 | 4.10.4_30-3.68.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP2 | xen | before 4.13.3_04-3.37.1 | 4.13.3_04-3.37.1 |
| SUSE:Linux Enterprise Module for Basesystem 15 SP3 | xen | before 4.14.2_06-3.12.1 | 4.14.2_06-3.12.1 |
| SUSE:Linux Enterprise Server 11 SP4-LTSS | xen | before 4.4.4_50-61.67.1 | 4.4.4_50-61.67.1 |
| SUSE:Linux Enterprise Server 12 SP2-BCL | xen | before 4.7.6_16-43.79.5 | 4.7.6_16-43.79.5 |
| SUSE:Linux Enterprise Software Development Kit 12 SP5 | xen | before 4.12.4_14-3.52.1 | 4.12.4_14-3.52.1 |
| SUSE:OpenStack Cloud 9 | xen | before 4.11.4_24-2.65.1 | 4.11.4_24-2.65.1 |
Same product
xen: all recordsOther 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, whi41Plan
- 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_host41Plan
- 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-2021-28699Aug 27, 2021 · inadequate grant-v2 status frames array bounds check The v2 grant table interface separates grant attributes from grant status.22Monitor
- ← EarlierCVE-2021-28700Aug 27, 2021 · xen/arm: No memory limit for dom0less domUs The dom0less feature allows an administrator to create multiple unprivileged domains directly fr20Monitor
- Later →CVE-2021-28702Oct 6, 2021 · PCI devices with RMRRs not deassigned correctly Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Res30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| alpine:xen | 4.13.3-r3 · Alpine:v3.11 | Package registry (OSV) |
| debian:xen | 4.14.3-1 · Debian:12 | Package registry (OSV) |
| opensuse:xen | 4.13.3_04-lp152.2.30.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| suse:xen | 4.4.4_50-61.67.1 · SUSE:Linux Enterprise Server 11 SP4-LTSS | Package 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.
No history yet (it accumulates with the daily EPSS job).
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 researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Julien GrallAmazon.'}]}}}
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).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-21-0764 · Sep 22, 2021(SUSE Linux Enterprise Güncellemesi)
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.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Local
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')CVSS vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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.
Attack patterns (CAPEC)
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (7 more)Show less
- xenbits.xen.org/xsa/advisory-384.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/
- security.gentoo.org/glsa/202208-23
- www.debian.org/security/2021/dsa-4977
- xenbits.xenproject.org/xsa/advisory-384.txt
Vendor advisories and official records. Exploit/PoC links are deliberately left out.