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Fencer Vulns
high 8.6

CVE-2021-28706 json

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hyperca…

published 2021-11-24 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15363

cvss
8.6
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.2%
EPSS 2.2% chance of exploitation in 30 days, percentile 82%
public exploits
0
none known

Summary

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Patch / fix

  • xen xen 4.12
  • xen Debian 14, Debian 13, Debian 12 4.14.3+32-g9de3671772-1

debian advisories DEBIAN-CVE-2021-28706

  • xen SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +3 more 4.12.4_16-3.57.1
  • xen SLE Module for Server Applications 15 SP3, SLE Module for Basesystem 15 SP3, SLE Micro 5.1 4.14.3_04-3.15.1
  • xen SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2, SLE Micro 5.0 4.13.4_02-3.40.1
  • xen SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 4.12.4_16-3.55.1
  • xen SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.9.4_24-3.97.1
  • 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 SLES 12 SP2-BCL 4.7.6_18-43.82.1

suse advisories SUSE-SU-2021:3977-1SUSE-SU-2021:3968-1SUSE-SU-2021:3888-1SUSE-SU-2021:3852-1SUSE-SU-2021:3851-1SUSE-SU-2021:14848-1

  • xen openSUSE Leap 15.3 4.14.3_04-3.15.1
  • xen openSUSE Leap 15.2 4.13.4_02-lp152.2.33.1

opensuse advisories openSUSE-SU-2021:3968-1openSUSE-SU-2021:1543-1

  • xen Alpine 3.12, Alpine 3.11 4.13.4-r2
  • xen Alpine 3.12 4.13.4-r3
  • xen Alpine 3.13 4.14.5-r0
  • xen Alpine 3.15, Alpine 3.14 4.15.2-r0

alpine advisories ALPINE-CVE-2021-28706

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

Exploit prediction

2.23% chance of exploitation in the next 30 days, higher than 82% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
NVD 2.0 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C

Affected products

  • Xen xen

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

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.