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Fencer Vulns
medium 5.5

CVE-2021-20255 json

A stack overflow via an infinite recursion vulnerability was found in the eepro100 i8255x device emulator of QEMU.

published 2021-03-09 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7693

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

A stack overflow via an infinite recursion vulnerability was found in the eepro100 i8255x device emulator of QEMU. This issue occurs while processing controller commands due to a DMA reentry issue. This flaw allows a guest user or process to consume CPU cycles or crash the QEMU process on the host, resulting in a denial of service. The highest threat from this vulnerability is to system availability.

Patch / fix

  • qemu Debian 14, Debian 13 1:8.1.0+ds-1

debian advisories DEBIAN-CVE-2021-20255

  • qemu SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 2.11.2-5.40.2
  • qemu SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +3 more 3.1.1.1-80.40.1
  • qemu SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.11.2-70.59.1
  • qemu SLES 12 SP2-BCL 2.6.2-41.73.1
  • 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 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 4.12.4_12-3.49.1

suse advisories SUSE-SU-2021:14848-1SUSE-SU-2021:3635-1SUSE-SU-2021:3614-1SUSE-SU-2021:3613-1SUSE-SU-2021:3575-1SUSE-SU-2021:3322-1

  • qemu openSUSE Leap 15.3 3.1.1.1-80.40.1
  • qemu openSUSE Leap 15.3 5.2.0-103.2
  • qemu openSUSE Leap 15.2 4.2.1-lp152.9.20.1
  • qemu-testsuite openSUSE Leap 15.2 4.2.1-lp152.9.20.1
  • qemu-linux-user openSUSE Leap 15.2 4.2.1-lp152.9.20.1
  • qemu openSUSE Leap 15.3 4.2.1-11.28.1

opensuse advisories openSUSE-SU-2021:3614-1openSUSE-SU-2021:2858-1openSUSE-SU-2021:1202-1openSUSE-SU-2021:2789-1

  • qemu Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 6.0.0-r1

alpine advisories ALPINE-CVE-2021-20255

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

  • qemu Azure Linux 3.0 6.2.0-18
  • qemu CBL-Mariner 2.0 6.2.0-2

azure linux advisories AZL-35149AZL-6829

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2021-20255 updated cvss 3.2

QEMU: net: eepro100: stack overflow via infinite recursion

  • Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 qemu-img, qemu-kvm, libcacard, qemu-img-ma, qemu-kvm-ma, qemu-kvm-rhev, +6 more Red Hat Enterprise Linux 8 qemu-img, qemu-kvm, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, qemu-guest-agent, +8 more Red Hat Enterprise Linux 8 Advanced Virtualization qemu-img, qemu-kvm, qemu-kiwi, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, +9 more 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
    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

0.41% chance of exploitation in the next 30 days, higher than 35% 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 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Affected products

  • n/a QEMU

Classification

Weakness
  • CWE-835 Loop with Unreachable Exit Condition
  • CWE-674 Uncontrolled Recursion

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.