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NVD / CVE Program· CNA redhat

CVE-2021-20255: A stack overflow via an infinite recursion vulnerability was found in the eepro100 i8255x device emulator of QEMU.

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.41% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: qemu (Alpine:v3.14) 6.0.0-r1; qemu (Debian:13) 1:8.1.0+ds-1; qemu (Debian:9) 1:2.8+dfsg-6+deb9u14.

Low priority for now. Upgrade to qemu (Alpine:v3.14) 6.0.0-r1; qemu (Debian:13) 1:8.1.0+ds-1; qemu (Debian:9) 1:2.8+dfsg-6+deb9u14 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Mar 9, 2021
Updated
Jun 16, 2026
EPSS
0.4% · 35th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
qemuqemu
debiandebian linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux9.0
  • qemu qemuall versions

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a QEMU

    • all versionsaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.14qemubefore 6.0.0-r16.0.0-r1
Debian:12qemufrom 0—
Debian:13qemubefore 1:8.1.0+ds-11:8.1.0+ds-1
Debian:9qemubefore 1:2.8+dfsg-6+deb9u141:2.8+dfsg-6+deb9u14
openSUSE:Leap 15.2qemubefore 4.2.1-lp152.9.20.14.2.1-lp152.9.20.1
openSUSE:Leap 15.2qemu-linux-userbefore 4.2.1-lp152.9.20.14.2.1-lp152.9.20.1
openSUSE:Leap 15.2qemu-testsuitebefore 4.2.1-lp152.9.20.14.2.1-lp152.9.20.1
openSUSE:Leap 15.3qemubefore 3.1.1.1-80.40.13.1.1.1-80.40.1
openSUSE:Leap 15.3qemubefore 4.2.1-11.28.14.2.1-11.28.1
openSUSE:Leap 15.3qemubefore 5.2.0-103.25.2.0-103.2
SUSE:HPE Helion OpenStack 8xenbefore 4.9.4_20-3.91.14.9.4_20-3.91.1
SUSE:Linux Enterprise High Performance Computing 15 SP1-ESPOSqemubefore 3.1.1.1-80.40.13.1.1.1-80.40.1
SUSE:Linux Enterprise High Performance Computing 15-ESPOSqemubefore 2.11.2-70.59.12.11.2-70.59.1
SUSE:Linux Enterprise Module for Basesystem 15 SP2qemubefore 4.2.1-11.28.14.2.1-11.28.1
SUSE:Linux Enterprise Module for Basesystem 15 SP3qemubefore 5.2.0-103.25.2.0-103.2
SUSE:Linux Enterprise Server 11 SP4-LTSSxenbefore 4.4.4_50-61.67.14.4.4_50-61.67.1
SUSE:Linux Enterprise Server 12 SP2-BCLqemubefore 2.6.2-41.73.12.6.2-41.73.1
SUSE:Linux Enterprise Server 12 SP2-BCLxenbefore 4.7.6_16-43.79.54.7.6_16-43.79.5
SUSE:Linux Enterprise Server 12 SP5qemubefore 3.1.1.1-57.23.1.1.1-57.2
SUSE:Linux Enterprise Software Development Kit 12 SP5xenbefore 4.12.4_12-3.49.14.12.4_12-3.49.1
SUSE:OpenStack Cloud 9qemubefore 2.11.2-5.40.22.11.2-5.40.2
SUSE:OpenStack Cloud 9xenbefore 4.11.4_20-2.60.14.11.4_20-2.60.1

Same product

qemu: all records

Other highest-scoring records for the same primary product.

  • CVE-2019-12928The QMP migrate command in QEMU version 4.0.0 and earlier is vulnerable to OS command injection, which allows the remote attacker to achieve
    60This week
  • CVE-2015-8556Local privilege escalation vulnerability in the Gentoo QEMU package before 2.5.0-r1.
    44Plan
  • CVE-2017-15118A stack-based buffer overflow vulnerability was found in NBD server implementation in qemu before 2.11 allowing a client to request an expor
    43Plan

Published before and after this one in the same product

  • ← EarlierCVE-2021-20203Feb 25, 2021 · An integer overflow issue was found in the vmxnet3 NIC emulator of the QEMU for versions up to v5.2.0.
    12Monitor
  • ← EarlierCVE-2021-20263Mar 9, 2021 · A flaw was found in the virtio-fs shared file system daemon (virtiofsd) of QEMU.
    13Monitor
  • Later →CVE-2021-3416Mar 18, 2021 · A potential stack overflow via infinite loop issue was found in various NIC emulators of QEMU in versions up to and including 5.2.0.
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:qemu6.0.0-r1 · Alpine:v3.14Package registry (OSV)
debian:qemu1:8.1.0+ds-1 · Debian:13Package registry (OSV)
opensuse:qemu4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:qemu-linux-user4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:qemu-testsuite4.2.1-lp152.9.20.1 · openSUSE:Leap 15.2Package registry (OSV)
suse:qemu4.2.1-11.28.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2Package registry (OSV)
suse:xen4.4.4_50-61.67.1 · SUSE:Linux Enterprise Server 11 SP4-LTSSPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records