dbcve.org
Out-of-bounds WriteWeakness · CWE-787

CVE-2026-0665

MEDIUM · 6.5 CVSS v3.1 Published 2026-02-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
67/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An off-by-one error was found in QEMU's KVM Xen guest support. A malicious guest could use this flaw to trigger out-of-bounds heap accesses in the QEMU process via the emulated Xen physdev hypercall interface, leading to a denial of service or potential memory corruption.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

An off-by-one error in QEMU's KVM Xen guest support allows a malicious guest to trigger out-of-bounds heap accesses via the emulated Xen physdev hypercall interface, potentially causing denial of service or memory corruption in the QEMU host process.

MitigationUpdate QEMU to the patched version that fixes the off-by-one error in the Xen physdev hypercall emulation. If running Xen guests under KVM, ensure QEMU is updated and test the physdev interface for regressions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed QEMU version
    Run 'qemu-system-x86_64 --version' or 'qemu-img --version' to determine the QEMU version installed on the host
    Affected if The installed version falls within the vulnerable range (prior to the patch for this off-by-one error in Xen physdev hypercall emulation)
  2. Confirm KVM kernel module is loaded
    Run 'lsmod | grep kvm' and check for 'kvm_intel' or 'kvm_amd' modules to verify KVM is active
    Affected if KVM is loaded and available, creating the condition for this vulnerability to be exploitable
  3. Check for active Xen guests running under KVM
    Run 'xl list' or 'virsh list --all' to enumerate running virtual machines and identify any that are Xen-based
    Affected if Any Xen virtual machines are running under QEMU/KVM, meaning the vulnerable Xen physdev hypercall interface is in use
  4. Verify QEMU is configured with Xen support
    Check QEMU build configuration by running 'qemu-system-x86_64 -help' 2>&1 | grep -i xen, or review the QEMU binary for xen capability: 'strings $(which qemu-system-x86_64) | grep -i xen'
    Affected if QEMU is built with Xen support enabled, which is required for the vulnerable code path to be present
  5. Inspect running QEMU processes with Xen guest parameters
    Run 'ps aux | grep qemu' to identify any qemu-system-x86_64 processes with Xen-related parameters such as '- xen-domid' or '- device xen-backend'
    Affected if A QEMU process is actively handling a Xen guest, meaning the vulnerable physdev hypercall emulation code is in use

A host is affected if it runs a vulnerable QEMU version with KVM enabled and is actively executing Xen guests, which causes the Xen physdev hypercall interface to be invoked.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update QEMU to the patched version that fixes the off-by-one error in the Xen physdev hypercall emulation. If running Xen guests under KVM, ensure QEMU is updated and test the physdev interface for regressions.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-0665 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-0665 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data