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Debian LinuxOperating system · Debian

CVE-2015-6855

HIGH · 7.5 CVSS v3.1 Published 2015-11-06
Fix available
A fix is available. Upgrade to after 2.4.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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
hw/ide/core.c in QEMU does not properly restrict the commands accepted by an ATAPI device, which allows guest users to cause a denial of service or possibly have unspecified other impact via certain IDE commands, as demonstrated by a WIN_READ_NATIVE_MAX command to an empty drive, which triggers a divide-by-zero error and instance crash.

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

In QEMU's hw/ide/core.c, the ATAPI device command handler lacks proper validation of incoming IDE commands. When a guest sends a WIN_READ_NATIVE_MAX command to an empty drive, the code attempts a division operation without checking for zero, causing a divide-by-zero error that crashes the QEMU instance.

MitigationApply the QEMU security patch that adds proper input validation to the ATAPI command handler, rejecting or safely handling invalid commands like WIN_READ_NATIVE_MAX on empty drives.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 7.0= 8.0= 9.0
FedoraOperating system
Affected:= 21= 22= 23
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 15.04
QemuApplication
Affected:<= 2.4.1
Linux Enterprise DesktopOperating system
Affected:= 12
Linux Enterprise ServerOperating system
Affected:= 12
EosOperating system
Affected:all versions

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 QEMU version
    Run 'qemu-system-x86_64 --version' or 'qemu-img --version' to determine the installed QEMU version number
    Affected if The installed version is <= 2.4.1 and matches one of the affected distribution packages (Debian 7.0/8.0/9.0, Fedora 21/22/23, Ubuntu 12.04/14.04/15.04, SUSE 12) or the upstream version is <= 2.4.1
  2. Verify IDE/ATAPI emulation is in use
    Review the QEMU command line or VM configuration for '-device ide-drive', '-device ide-cd', or similar IDE/ATAPI device definitions
    Affected if IDE or ATAPI emulated devices (ide-drive, ide-cd, ide-hd, piix3-ide) are assigned to the guest VM
  3. Identify virtual disks on IDE controllers
    Examine the VM configuration or libvirt domain XML (if using libvirt) for disk devices with bus type 'ide' or 'ata'
    Affected if Any virtual disk or CDROM is connected to an IDE controller in the VM configuration
  4. Check for empty or no-media IDE drives
    Review the disk configuration for IDE devices that have no media path defined, or verify if any IDE cdrom/drive could be accessed empty by the guest
    Affected if An IDE drive or CDROM device is configured without media or with an empty/cjected media

A system is affected if it runs QEMU <= 2.4.1 with IDE/ATAPI emulation enabled and has an empty or media-less IDE drive accessible to the guest, allowing a malicious guest to trigger the divide-by-zero by issuing WIN_READ_NATIVE_MAX.

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
Upgrade available Upgrade to a release after 2.4.1
Interim mitigation

Apply the QEMU security patch that adds proper input validation to the ATAPI command handler, rejecting or safely handling invalid commands like WIN_READ_NATIVE_MAX on empty drives.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,648.

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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-2015-6855 in production — separate from our analysis above.

No notes yet

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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