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Fencer Vulns
medium 6.5

CVE-2021-3975 json

A use-after-free flaw was found in libvirt.

published 2022-08-23 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-27180

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.6%
EPSS 1.6% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

A use-after-free flaw was found in libvirt. The qemuMonitorUnregister() function in qemuProcessHandleMonitorEOF is called using multiple threads without being adequately protected by a monitor lock. This flaw could be triggered by the virConnectGetAllDomainStats API when the guest is shutting down. An unprivileged client with a read-only connection could use this flaw to perform a denial of service attack by causing the libvirt daemon to crash.

Patch / fix

  • redhat libvirt 7.1.0
  • libvirt Debian 14, Debian 13, Debian 12 7.6.0-1

debian advisories DEBIAN-CVE-2021-3975

  • libvirt Ubuntu 18.04 LTS 4.0.0-1ubuntu8.21
  • libvirt Ubuntu 20.04 LTS 6.0.0-0ubuntu8.16
  • libvirt Ubuntu 22.04 LTS 7.6.0-0ubuntu3

ubuntu advisories UBUNTU-CVE-2021-3975

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 20210217-1.module+el8.6.0+14480+c0a3aa0f
  • hivex RHEL 8 1.3.18-23.module+el8.6.0+14480+c0a3aa0f
  • netcf RHEL 8 0.2.8-12.module+el8.6.0+14480+c0a3aa0f
  • swtpm RHEL 8 0.7.0-1.20211109gitb79fd91.module+el8.6.0+14480+c0a3aa0f
  • libnbd RHEL 8 1.6.0-5.module+el8.6.0+14480+c0a3aa0f
  • nbdkit RHEL 8 1.24.0-4.module+el8.6.0+14480+c0a3aa0f
  • libtpms RHEL 8 0.9.1-0.20211126git1ff6fe1f43.module+el8.6.0+14480+c0a3aa0f
  • libvirt RHEL 8 8.0.0-5.module+el8.6.0+14480+c0a3aa0f

red hat advisories RHSA-2022:1759RHBA-2021:4684

  • libvirt SLES 15 SP2-BCL, SLE Real Time 15 SP2, SLE Micro 5.0 +8 more 6.0.0-13.24.1
  • libvirt SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +3 more 5.1.0-17.1
  • libvirt SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.0.0-8.26.1
  • libvirt SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 3.3.0-5.49.1
  • libvirt SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 5.1.0-13.28.2
  • libvirt SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.0.0-9.40.1

suse advisories SUSE-SU-2022:0045-2SUSE-SU-2022:0128-1SUSE-SU-2022:0045-1SUSE-SU-2022:0042-1SUSE-SU-2022:0041-1SUSE-SU-2022:0032-1

  • SLOF AlmaLinux 8 20210217-1.module_el8.6.0+2880+7d9e3703
  • hivex AlmaLinux 8 1.3.18-23.module_el8.6.0+2880+7d9e3703
  • netcf AlmaLinux 8 0.2.8-12.module_el8.6.0+2880+7d9e3703
  • swtpm AlmaLinux 8 0.7.0-1.20211109gitb79fd91.module_el8.6.0+2880+7d9e3703
  • libnbd AlmaLinux 8 1.6.0-5.module_el8.6.0+2880+7d9e3703
  • nbdkit AlmaLinux 8 1.24.0-4.module_el8.6.0+2880+7d9e3703
  • libtpms AlmaLinux 8 0.9.1-0.20211126git1ff6fe1f43.module_el8.6.0+2880+7d9e3703
  • libvirt AlmaLinux 8 8.0.0-5.module_el8.6.0+2880+7d9e3703

almalinux advisories ALSA-2022:1759

  • hivex Rocky Linux 8 1.3.18-23.module+el8.7.0+1084+97b81f61
  • hivex Rocky Linux 8 1.3.18-23.module+el8.6.0+847+b490afdd
  • 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
  • swtpm Rocky Linux 8 0.7.0-1.20211109gitb79fd91.module+el8.6.0+847+b490afdd
  • libnbd Rocky Linux 8 1.6.0-5.module+el8.7.0+1084+97b81f61
  • libnbd Rocky Linux 8 1.6.0-5.module+el8.6.0+847+b490afdd

rocky linux advisories RLSA-2022:1759

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-2021-3975 updated cvss 5.3

libvirt: segmentation fault during VM shutdown can lead to vdsm hang

  • Red Hat Enterprise Linux 6 libvirt, libvirt-client, libvirt-python, libvirt-lock-sanlock Red Hat Enterprise Linux 7 libvirt, libvirt-nss, libvirt-libs, libvirt-admin, libvirt-client, libvirt-daemon, +24 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 Advanced Virtualization libvirt, libvirt-nss, libvirt-libs, libvirt-admin, libvirt-client, libvirt-daemon, +22 more
    affected: no fix available “Fix deferred”
  • Red Hat Advanced Virtualization CodeReady Builder for RHEL 8.5.0 netcf 0.2.8-12.module+el8.4.0+8855+a9e237a9, libnbd 1.6.0-4.module+el8.5.0+11638+3d8f9850, hivex 1.3.18-22.module+el8.5.0+12087+2208d04c, libvirt 7.6.0-6.module+el8.5.0+13051+7ddbe958, nbdfuse 1.6.0-4.module+el8.5.0+11638+3d8f9850, seabios 1.14.0-1.module+el8.4.0+8855+a9e237a9, +38 more Red Hat Advanced Virtualization for RHEL 8.5.0 netcf 0.2.8-12.module+el8.4.0+8855+a9e237a9, libnbd 1.6.0-4.module+el8.5.0+11638+3d8f9850, nbdkit 1.24.0-1.module+el8.4.0+9341+96cf2672, hivex 1.3.18-22.module+el8.5.0+12087+2208d04c, libvirt 7.6.0-6.module+el8.5.0+13051+7ddbe958, nbdfuse 1.6.0-4.module+el8.5.0+11638+3d8f9850, +106 more
    fixed: vendor fix RHBA-2021:4684
  • Red Hat Enterprise Linux AppStream (v. 8) libnbd 1.6.0-5.module+el8.6.0+14480+c0a3aa0f, netcf 0.2.8-12.module+el8.6.0+14480+c0a3aa0f, hivex 1.3.18-23.module+el8.6.0+14480+c0a3aa0f, libvirt 8.0.0-5.module+el8.6.0+14480+c0a3aa0f, nbdfuse 1.6.0-5.module+el8.6.0+14480+c0a3aa0f, nbdkit 1.24.0-4.module+el8.6.0+14480+c0a3aa0f, +104 more Red Hat Enterprise Linux CRB (v. 8) libnbd 1.6.0-5.module+el8.6.0+14480+c0a3aa0f, netcf 0.2.8-12.module+el8.6.0+14480+c0a3aa0f, hivex 1.3.18-23.module+el8.6.0+14480+c0a3aa0f, libvirt 8.0.0-5.module+el8.6.0+14480+c0a3aa0f, nbdfuse 1.6.0-5.module+el8.6.0+14480+c0a3aa0f, SLOF 20210217-1.module+el8.6.0+14480+c0a3aa0f, +38 more
    fixed: vendor fix RHSA-2022:1759
  • Red Hat Enterprise Linux 9 libvirt, libvirt-nss, libvirt-libs, libvirt-client, libvirt-daemon, libvirt-ssh-proxy, +25 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

1.64% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • n/a libvirt

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.