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Fencer Vulns
high 7.8

CVE-2021-28701 json

Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory.

published 2021-09-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15358

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

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.

Patch / fix

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

debian advisories DEBIAN-CVE-2021-28701

  • xen SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +3 more 4.12.4_16-3.57.1
  • xen SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.11.4_24-2.65.1
  • xen SLES for SAP 15, SLE High Performance Computing 15-LTSS, SLE High Performance Computing 15-ESPOS 4.10.4_30-3.68.1
  • xen SLE Module for Server Applications 15 SP3, SLE Module for Basesystem 15 SP3, SLE Micro 5.1 4.14.2_06-3.12.1
  • 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_22-3.94.2
  • xen SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 4.12.4_14-3.52.1
  • xen SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 4.13.3_04-3.37.1

suse advisories SUSE-SU-2021:3977-1SUSE-SU-2021:14848-1SUSE-SU-2021:3849-1SUSE-SU-2021:3842-1SUSE-SU-2021:3140-2SUSE-SU-2021:3322-1

  • xen openSUSE Leap 15.2 4.13.3_04-lp152.2.30.1
  • xen openSUSE Leap 15.3 4.14.2_06-3.12.1

opensuse advisories openSUSE-SU-2021:1301-1openSUSE-SU-2021:3140-1

  • xen Alpine 3.12, Alpine 3.11 4.13.3-r3
  • xen Alpine 3.13 4.14.2-r1
  • xen Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 4.15.0-r3

alpine advisories ALPINE-CVE-2021-28701

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-2021-28701 updated cvss 7.8

xen: another race in XENMAPSPACE_grant_table handling

  • 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

0.27% 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:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD 2.0 4.4 AV:L/AC:M/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.