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Fencer Vulns
medium 6.0

CVE-2021-20221 json

An out-of-bounds heap buffer access issue was found in the ARM Generic Interrupt Controller emulator of QEMU up to and including qemu 4.2.0…

published 2021-05-13 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7662

cvss
6.0
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 25%
public exploits
0
none known

Summary

An out-of-bounds heap buffer access issue was found in the ARM Generic Interrupt Controller emulator of QEMU up to and including qemu 4.2.0on aarch64 platform. The issue occurs because while writing an interrupt ID to the controller memory area, it is not masked to be 4 bits wide. It may lead to the said issue while updating controller state fields and their subsequent processing. A privileged guest user may use this flaw to crash the QEMU process on the host resulting in DoS scenario.

Patch / fix

  • qemu Debian 14, Debian 13, Debian 12 1:5.2+dfsg-4

debian advisories DEBIAN-CVE-2021-20221

  • qemu Ubuntu 18.04 LTS 1:2.11+dfsg-1ubuntu7.37
  • qemu Ubuntu 20.04 LTS 1:4.2-3ubuntu6.17
  • qemu Ubuntu Pro 14.04 LTS 2.0.0+dfsg-2ubuntu1.47+esm6
  • qemu Ubuntu Pro 16.04 LTS 1:2.5+dfsg-5ubuntu10.51+esm4

ubuntu advisories UBUNTU-CVE-2021-20221

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • SLOF RHEL 8 20191022-3.git899d9883.module+el8.3.0+6423+e4cb6418
  • hivex RHEL 8 1.3.18-21.module+el8.4.0+10770+19c037f9
  • netcf RHEL 8 0.2.8-12.module+el8.1.0+4066+0f1aadab
  • libnbd RHEL 8 1.2.2-1.module+el8.3.0+7353+9de0a3cc
  • nbdkit RHEL 8 1.16.2-4.module+el8.3.0+6922+fd575af8
  • libvirt RHEL 8 6.0.0-35.1.module+el8.4.0+11273+64eb94ef
  • nbdfuse RHEL 8 1.2.2-1.module+el8.3.0+7353+9de0a3cc
  • seabios RHEL 8 1.13.0-2.module+el8.3.0+7353+9de0a3cc

red hat advisories RHSA-2021:3061RHSA-2021:2521RHSA-2021:1125

  • kvm SLE Point of Sale 11 SP3 1.4.2-53.41.1
  • qemu SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 2.9.1-6.50.1
  • qemu SLES 12 SP2-BCL 2.6.2-41.65.1
  • qemu SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 3.1.1.1-9.24.3
  • qemu SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.11.2-9.43.1
  • qemu SLES for SAP 12 SP5, SLES 12 SP5 3.1.1.1-48.2
  • qemu SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 2.11.2-5.29.1
  • qemu SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2 4.2.1-11.13.1

suse advisories SUSE-SU-2021:14774-1SUSE-SU-2021:14772-1SUSE-SU-2021:1894-1SUSE-SU-2021:1829-1SUSE-SU-2021:1245-1SUSE-SU-2021:1244-1

  • qemu openSUSE Tumbleweed 6.1.0-32.1
  • qemu openSUSE Leap 15.2 4.2.1-lp152.9.9.2
  • qemu-testsuite openSUSE Leap 15.2 4.2.1-lp152.9.9.5
  • qemu-linux-user openSUSE Leap 15.2 4.2.1-lp152.9.9.3

opensuse advisories openSUSE-SU-2024:11287-1openSUSE-SU-2021:0363-1

  • netcf AlmaLinux 8 0.2.8-12.module_el8.5.0+2608+72063365
  • netcf AlmaLinux 8 0.2.8-12.module_el8.6.0+2880+7d9e3703
  • libnbd AlmaLinux 8 1.2.2-1.module_el8.5.0+2608+72063365
  • nbdkit AlmaLinux 8 1.16.2-4.module_el8.5.0+2608+72063365
  • nbdfuse AlmaLinux 8 1.2.2-1.module_el8.5.0+2608+72063365
  • seabios AlmaLinux 8 1.13.0-2.module_el8.5.0+2608+72063365
  • sgabios AlmaLinux 8 1:0.20170427git-3.module_el8.5.0+2608+72063365
  • sgabios AlmaLinux 8 1:0.20170427git-3.module_el8.6.0+2880+7d9e3703

almalinux advisories ALSA-2021:3061

  • hivex Rocky Linux 8 1.3.18-21.module+el8.4.0+642+7e26f5e1
  • hivex Rocky Linux 8 1.3.18-21.module+el8.5.0+670+c4aa478c
  • netcf Rocky Linux 8 0.2.8-12.module+el8.7.0+1084+97b81f61
  • netcf Rocky Linux 8 0.2.8-12.module+el8.4.0+534+4680a14e
  • netcf Rocky Linux 8 0.2.8-12.module+el8.6.0+847+b490afdd
  • libnbd Rocky Linux 8 1.2.2-1.module+el8.4.0+534+4680a14e
  • nbdkit Rocky Linux 8 1.16.2-4.module+el8.4.0+534+4680a14e
  • libvirt Rocky Linux 8 6.0.0-35.1.module+el8.4.0+642+7e26f5e1

rocky linux advisories RLSA-2021:3061

  • qemu Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 5.0.0-r0

alpine advisories ALPINE-CVE-2021-20221

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-2021-20221 updated cvss 2.5

qemu: out-of-bound heap buffer access via an interrupt ID field

  • Red Hat Enterprise Linux 7 qemu-img-ma, qemu-kvm-ma, qemu-img-rhev, qemu-kvm-rhev, qemu-kvm-tools-ma, qemu-kvm-common-ma, +2 more
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 8 Advanced Virtualization qemu-img, qemu-kvm, qemu-kiwi, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, +9 more
    affected: no fix available
  • Red Hat OpenStack Platform 10 (Newton) qemu-img-rhev, qemu-kvm-rhev, qemu-kvm-tools-rhev, qemu-kvm-common-rhev Red Hat OpenStack Platform 13 (Queens) qemu-img-rhev, qemu-kvm-rhev, qemu-kvm-tools-rhev, qemu-kvm-common-rhev
    affected: no fix planned “Out of support scope”
  • Red Hat Advanced Virtualization CodeReady Builder for RHEL 8.2.1 libnbd 1.2.2-1.module+el8.2.0+5644+32ac38d4, netcf 0.2.8-12.module+el8.2.0+4793+b09dd2fb, hivex 1.3.18-20.module+el8.2.0+5588+63a201c3, nbdfuse 1.2.2-1.module+el8.2.0+5644+32ac38d4, seabios 1.13.0-2.module+el8.2.1+7284+aa32a2c4, libiscsi 1.18.0-8.module+el8.2.0+4793+b09dd2fb, +45 more
    fixed: vendor fix RHSA-2021:2521
  • Red Hat Advanced Virtualization CodeReady Builder for RHEL 8.3.1 libnbd 1.4.0-2.module+el8.3.0+7998+6ff5e5ab, netcf 0.2.8-12.module+el8.3.0+6124+819ee737, hivex 1.3.18-20.module+el8.3.0+6124+819ee737, nbdfuse 1.4.0-2.module+el8.3.0+7998+6ff5e5ab, seabios 1.14.0-1.module+el8.3.0+7638+07cf13d2, libiscsi 1.18.0-8.module+el8.3.0+6124+819ee737, +40 more
    fixed: vendor fix RHSA-2021:1125
  • Red Hat Advanced Virtualization for RHEL 8.2.1 libnbd 1.2.2-1.module+el8.2.0+5644+32ac38d4, netcf 0.2.8-12.module+el8.2.0+4793+b09dd2fb, hivex 1.3.18-20.module+el8.2.0+5588+63a201c3, nbdfuse 1.2.2-1.module+el8.2.0+5644+32ac38d4, nbdkit 1.16.2-4.module+el8.2.1+6710+effcb1df, seabios 1.13.0-2.module+el8.2.1+7284+aa32a2c4, +96 more
    fixed: vendor fix RHSA-2021:2521
  • Red Hat Advanced Virtualization for RHEL 8.3.1 libnbd 1.4.0-2.module+el8.3.0+7998+6ff5e5ab, netcf 0.2.8-12.module+el8.3.0+6124+819ee737, hivex 1.3.18-20.module+el8.3.0+6124+819ee737, nbdfuse 1.4.0-2.module+el8.3.0+7998+6ff5e5ab, nbdkit 1.22.0-2.module+el8.3.0+8203+18ecf00e, seabios 1.14.0-1.module+el8.3.0+7638+07cf13d2, +103 more
    fixed: vendor fix RHSA-2021:1125
  • Red Hat CodeReady Linux Builder (v. 8) libnbd 1.2.2-1.module+el8.3.0+7353+9de0a3cc, netcf 0.2.8-12.module+el8.1.0+4066+0f1aadab, nbdfuse 1.2.2-1.module+el8.3.0+7353+9de0a3cc, hivex 1.3.18-21.module+el8.4.0+10770+19c037f9, seabios 1.13.0-2.module+el8.3.0+7353+9de0a3cc, libiscsi 1.18.0-8.module+el8.1.0+4066+0f1aadab, +39 more Red Hat Enterprise Linux AppStream (v. 8) libnbd 1.2.2-1.module+el8.3.0+7353+9de0a3cc, netcf 0.2.8-12.module+el8.1.0+4066+0f1aadab, nbdfuse 1.2.2-1.module+el8.3.0+7353+9de0a3cc, nbdkit 1.16.2-4.module+el8.3.0+6922+fd575af8, hivex 1.3.18-21.module+el8.4.0+10770+19c037f9, seabios 1.13.0-2.module+el8.3.0+7353+9de0a3cc, +88 more
    fixed: vendor fix RHSA-2021:3061
show 1 more
  • Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32 Red Hat Enterprise Linux 7 qemu-img, qemu-kvm, libcacard, qemu-kvm-tools, libcacard-tools, qemu-kvm-common, +1 more
    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

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.0 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • n/a qemu

Classification

Weakness

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.