Skip to content
Fencer Vulns
high 7.8

CVE-2021-28697 json

grant table v2 status pages may remain accessible after de-allocation Guest get permitted access to certain Xen-owned pages of memory.

published 2021-08-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15354

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 18%
public exploits
0
none known

Summary

grant table v2 status pages may remain accessible after de-allocation Guest get 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, get de-allocated when a guest switched (back) from v2 to v1. The freeing of such pages requires that the hypervisor know where in the guest these pages were mapped. The hypervisor tracks only one use within guest space, but racing requests from the guest to insert mappings of these pages may result in any of them to become mapped in multiple locations. Upon switching back from v2 to v1, the guest would then retain access to a page that was freed and perhaps re-used for other purposes.

Patch / fix

  • xen Debian 14, Debian 13, Debian 12 4.14.3-1

debian advisories DEBIAN-CVE-2021-28697

  • xen SLES 12 SP2-BCL 4.7.6_16-43.79.5
  • xen SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.9.4_20-3.91.1
  • xen SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.11.4_20-2.60.1
  • xen SLES for SAP 15, SLE High Performance Computing 15-LTSS, SLE High Performance Computing 15-ESPOS 4.10.4_26-3.61.1
  • xen SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 4.12.4_12-3.52.1
  • xen SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 4.12.4_12-3.49.1
  • xen SLE Module for Server Applications 15 SP3, SLE Module for Basesystem 15 SP3 4.14.2_04-3.9.1
  • xen SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 4.13.3_02-3.34.1

suse advisories SUSE-SU-2021:14848-1SUSE-SU-2021:3322-1SUSE-SU-2021:2957-1SUSE-SU-2021:2955-1SUSE-SU-2021:2943-1SUSE-SU-2021:2925-1

  • xen openSUSE Leap 15.2 4.13.3_02-lp152.2.27.1
  • xen openSUSE Leap 15.3 4.14.2_04-3.9.1

opensuse advisories openSUSE-SU-2021:1236-1openSUSE-SU-2021:2923-1

  • xen Alpine 3.12, Alpine 3.11 4.13.3-r2
  • xen Alpine 3.13 4.14.2-r0
  • xen Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 4.15.0-r2

alpine advisories ALPINE-CVE-2021-28697

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-28697 updated cvss 6.8

xen: malicious guest may be able to elevate its privileges leads to DoS

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.26% chance of exploitation in the next 30 days, higher than 18% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Xen xen

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.