Skip to content
Fencer Vulns
medium 6.1

CVE-2021-3507 json

A heap buffer overflow was found in the floppy disk emulator of QEMU up to 6.0.0 (including).

published 2021-05-06 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26826

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

A heap buffer overflow was found in the floppy disk emulator of QEMU up to 6.0.0 (including). It could occur in fdctrl_transfer_handler() in hw/block/fdc.c while processing DMA read data transfers from the floppy drive to the guest system. A privileged guest user could use this flaw to crash the QEMU process on the host resulting in DoS scenario, or potential information leakage from the host memory.

Patch / fix

  • qemu Debian 14, Debian 13, Debian 12 1:7.1+dfsg-1

debian advisories DEBIAN-CVE-2021-3507

  • qemu Ubuntu 18.04 LTS 1:2.11+dfsg-1ubuntu7.40
  • qemu Ubuntu 20.04 LTS 1:4.2-3ubuntu6.23
  • qemu Ubuntu 22.04 LTS 1:6.2+dfsg-2ubuntu6.2
  • 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-2021-3507

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+el8.7.0+16689+53d59bc2
  • hivex RHEL 8 1.3.18-23.module+el8.7.0+16689+53d59bc2
  • netcf RHEL 8 0.2.8-12.module+el8.7.0+16689+53d59bc2
  • swtpm RHEL 8 0.7.0-4.20211109gitb79fd91.module+el8.7.0+16689+53d59bc2
  • libnbd RHEL 8 1.6.0-5.module+el8.7.0+16689+53d59bc2
  • nbdkit RHEL 8 1.24.0-4.module+el8.7.0+16689+53d59bc2
  • libtpms RHEL 8 0.9.1-1.20211126git1ff6fe1f43.module+el8.7.0+16689+53d59bc2
  • libvirt RHEL 8 8.0.0-10.module+el8.7.0+16689+53d59bc2

red hat advisories RHSA-2022:7472RHSA-2022:7967

  • qemu SLE Module for Server Applications 15 SP4, SLE Module for Basesystem 15 SP4, SLE Micro 5.4 +3 more 6.2.0-150400.37.14.2
  • qemu-testsuite openSUSE Leap 15.4 6.2.0-150400.37.14.1
  • qemu-linux-user openSUSE Leap 15.4 6.2.0-150400.37.14.1
  • qemu SLES for SAP 15 SP2, SLES 15 SP2-LTSS, SLE High Performance Computing 15 SP2-LTSS +2 more 4.2.1-150200.72.2
  • qemu SLES for SAP 15 SP3, SLES 15 SP3-LTSS, SLE Real Time 15 SP3 +7 more 5.2.0-150300.121.2
  • qemu SLES for SAP 12 SP5, SLES 12 SP5 3.1.1.1-66.1
  • qemu SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +4 more 3.1.1.1-150100.80.43.2

suse advisories SUSE-SU-2023:0879-2SUSE-SU-2023:0879-1SUSE-SU-2023:0878-1SUSE-SU-2023:0840-1SUSE-SU-2023:0761-1SUSE-SU-2022:3768-1

  • qemu-kvm AlmaLinux 9 17:7.0.0-13.el9
  • qemu-img AlmaLinux 9 17:7.0.0-13.el9
  • qemu-kvm-core AlmaLinux 9 17:7.0.0-13.el9
  • qemu-kvm-tools AlmaLinux 9 17:7.0.0-13.el9
  • qemu-pr-helper AlmaLinux 9 17:7.0.0-13.el9
  • qemu-kvm-common AlmaLinux 9 17:7.0.0-13.el9
  • qemu-guest-agent AlmaLinux 9 17:7.0.0-13.el9
  • qemu-kvm-audio-pa AlmaLinux 9 17:7.0.0-13.el9

almalinux advisories ALSA-2022:7967

  • qemu-kvm Rocky Linux 9 7:7.0.0-13.el9
  • 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 0.7.0-4.20211109gitb79fd91.module+el8.7.0+1084+97b81f61
  • libnbd Rocky Linux 8 1.6.0-5.module+el8.7.0+1084+97b81f61

rocky linux advisories RLSA-2022:7967RLSA-2022:7472

  • qemu Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 6.1.0-r0

alpine advisories ALPINE-CVE-2021-3507

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-2021-3507 updated cvss 4.6

QEMU: fdc: heap buffer overflow in DMA read data transfers

  • 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-img-ma, qemu-kvm-ma, qemu-kvm-rhev, +6 more
    affected: no fix planned “Out of support scope”
  • 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, no fix planned “Will not fix”
  • 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 CodeReady Linux Builder (v. 8) libnbd 1.6.0-5.module+el8.7.0+16689+53d59bc2, netcf 0.2.8-12.module+el8.7.0+16689+53d59bc2, hivex 1.3.18-23.module+el8.7.0+16689+53d59bc2, nbdfuse 1.6.0-5.module+el8.7.0+16689+53d59bc2, SLOF 20210217-1.module+el8.7.0+16689+53d59bc2, libvirt 8.0.0-10.module+el8.7.0+16689+53d59bc2, +38 more Red Hat Enterprise Linux AppStream (v. 8) libnbd 1.6.0-5.module+el8.7.0+16689+53d59bc2, netcf 0.2.8-12.module+el8.7.0+16689+53d59bc2, hivex 1.3.18-23.module+el8.7.0+16689+53d59bc2, nbdfuse 1.6.0-5.module+el8.7.0+16689+53d59bc2, nbdkit 1.24.0-4.module+el8.7.0+16689+53d59bc2, SLOF 20210217-1.module+el8.7.0+16689+53d59bc2, +104 more
    fixed: vendor fix RHSA-2022:7472
  • Red Hat Enterprise Linux AppStream (v. 9) qemu-img 7.0.0-13.el9, qemu-kvm 7.0.0-13.el9, qemu-kvm-core 7.0.0-13.el9, qemu-kvm-tools 7.0.0-13.el9, qemu-pr-helper 7.0.0-13.el9, qemu-kvm-common 7.0.0-13.el9, +15 more
    fixed: vendor fix RHSA-2022:7967

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

0.49% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=1951118 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 6.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L
NVD 2.0 3.6 AV:L/AC:L/Au:N/C:P/I:N/A:P

Affected products

  • n/a QEMU

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
  • CWE-787 Out-of-bounds Write

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.