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CVE Record

CVE-2021-4206: A flaw was found in the QXL display device emulation in QEMU.

A flaw was found in the QXL display device emulation in QEMU. An integer overflow in the cursor_alloc() function can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. This flaw allows a malicious privileged guest user to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a QEMU virtualization flaw in QXL display emulation. A privileged user inside a guest VM could crash the QEMU process on the host, and the source description says arbitrary code execution in that process may be possible. Business risk is highest where untrusted or tenant-managed guests run on affected QEMU builds.

Executive priority

Treat this as a high-priority virtualization maintenance issue, especially for shared hosting, lab, and tenant VM environments. There is no provided evidence of active exploitation, but the possible host-side impact makes delayed patching risky where guest administrators are not fully trusted.

Technical view

CVE-2021-4206 is an integer overflow in QEMU QXL cursor_alloc(). The overflow may under-allocate a cursor object and lead to a heap-based buffer overflow. The reported impact is host-side QEMU process crash or potential code execution in the QEMU process context by a malicious privileged guest user.

Likely exposure

Exposure appears limited to environments running affected QEMU or qemu-kvm with QXL display device emulation. The bundle lists qemu-kvm 7.0.0 and includes Debian, Gentoo, Red Hat, and NetApp references. Product-specific affected versions beyond the bundle are not established here.

Exploitation context

The source bundle does not show CISA KEV listing or cited active exploitation. The attacker position is significant: a malicious privileged guest user. Impact can cross the guest-host operational boundary by crashing host QEMU and may allow code execution in the QEMU process.

Researcher notes

The key primitive is CWE-190 integer overflow leading to undersized allocation and heap overflow in QXL cursor handling. Evidence in the bundle supports privileged guest-to-QEMU impact, not general unauthenticated network exposure. Patch details and exploit maturity are incomplete in the provided sources.

Mitigation direction

  • Apply vendor QEMU or qemu-kvm security updates from relevant advisories.
  • Check Red Hat, Debian, Gentoo, NetApp, or platform vendor guidance for fixed versions.
  • Prioritize hosts running untrusted or multi-tenant guest workloads.
  • Where patch timing is delayed, reduce privileged guest access where operationally feasible.

Validation and detection

  • Inventory QEMU and qemu-kvm package versions on virtualization hosts.
  • Identify VMs configured with QXL display emulation.
  • Confirm vendor security updates reference CVE-2021-4206 or bundled QEMU fixes.
  • Review host monitoring for unexplained QEMU process crashes.
  • Track affected appliance or storage products against NetApp guidance where applicable.
Prepared
Confidence
medium
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-190: Exact CWE lookup

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-4206 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/aQEMUqemu-kvm 7.0.0Listed
Weakness

CWE details

CWE-190

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-190 · source CWE mapping

Integer Overflow or Wraparound

Integer Overflow or Wraparound represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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