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Fencer Vulns
medium 5.5

CVE-2021-28698 json

long running loops in grant table handling In order to properly monitor resource use, Xen maintains information on the grant mappings a dom…

published 2021-08-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-15355

cvss
5.5
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 28%
public exploits
0
none known

Summary

long running loops in grant table handling In order to properly monitor resource use, Xen maintains information on the grant mappings a domain may create to map grants offered by other domains. In the process of carrying out certain actions, Xen would iterate over all such entries, including ones which aren't in use anymore and some which may have been created but never used. If the number of entries for a given domain is large enough, this iterating of the entire table may tie up a CPU for too long, starving other domains or causing issues in the hypervisor itself. Note that a domain may map its own grants, i.e. there is no need for multiple domains to be involved here. A pair of "cooperating" guests may, however, cause the effects to be more severe.

Patch / fix

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

debian advisories DEBIAN-CVE-2021-28698

  • 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-2021-28698

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-2021-28698 updated cvss 6.2

xen: malicious kernels lead 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

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.9 AV:L/AC:L/Au:N/C:N/I:N/A:C

Affected products

  • Xen xen

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition

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.