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Linux KernelOperating system · Linux

CVE-2015-8551

MEDIUM · 6.0 CVSS v3.1 Published 2016-04-13
Fix available
A fix is available. Upgrade to after 4.3.6 or later.
See remediation →
62/100
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
The PCI backend driver in Xen, when running on an x86 system and using Linux 3.1.x through 4.3.x as the driver domain, allows local guest administrators to hit BUG conditions and cause a denial of service (NULL pointer dereference and host OS crash) by leveraging a system with access to a passed-through MSI or MSI-X capable physical PCI device and a crafted sequence of XEN_PCI_OP_* operations, aka "Linux pciback missing sanity checks."

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

The PCI backend driver (pciback) in Xen for x86 systems running Linux 3.1.x-4.3.x as the driver domain lacks sanity checks when handling XEN_PCI_OP_* operations. Local guest administrators with access to passed-through MSI/MSI-X capable PCI devices can trigger NULL pointer dereferences, causing BUG conditions and host OS crashes.

MitigationApply the upstream fix (sanity checks in pciback driver) by upgrading the driver domain Linux kernel to a version beyond 4.3, or apply vendor-specific patches. Alternatively, ensure untrusted guests cannot access PCI passthrough capabilities if patching is not immediately feasible.

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
Linux KernelOperating system
Affected:>= 3.1, <= 3.1.10>= 4.3.0, <= 4.3.6
Debian LinuxOperating system
Affected:= 7.0= 8.0
OpensuseOperating system
Affected:= 13.1
Linux Enterprise DesktopOperating system
Affected:= 11= 12
Linux Enterprise Real Time ExtensionOperating system
Affected:= 11= 12
Linux Enterprise ServerOperating system
Affected:= 11= 12
Linux Enterprise Software Development KitOperating system
Affected:= 11= 12
Linux Enterprise Workstation ExtensionOperating system
Affected:= 12

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
High
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/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. Verify Xen hypervisor is in use
    Run 'xl info' or 'xm info' or check for Xen kernel boot parameters (xen_` in uname -a output)
    Affected if System is not running Xen hypervisor - this vulnerability only affects Xen environments with pciback driver
  2. Confirm kernel version is within affected range
    Run 'uname -r' and compare to: 3.1.x (up to 3.1.10) or 4.3.x (up to 4.3.6). Example: 'uname -r' returns 4.3.5 means affected
    Affected if Kernel version is between 3.1 and 3.1.10 inclusive, or between 4.3.0 and 4.3.6 inclusive
  3. Determine if PCI passthrough is enabled
    Check for passed-through PCI devices in guest configurations: 'xl pci-assignable-list' or look for 'pci' device entries in guest config files under /etc/xen/
    Affected if Guest domains have PCI devices assigned via passthrough - the vulnerability is only exploitable when guests have access to passed-through PCI devices
  4. Verify pciback driver is loaded
    Run 'lsmod | grep pciback' or check 'xl pci-list <guestname>' to see if any guest has access to PCI devices requiring the pciback backend
    Affected if pciback module is loaded and handling PCI passthrough operations for guest domains with MSI/MSI-X capable PCI devices

A system is affected if it runs Xen with a vulnerable kernel (3.1-3.1.10 or 4.3.0-4.3.6) and has guest domains with assigned PCI devices that use MSI/MSI-X interrupts.

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 4.3.6
Interim mitigation

Apply the upstream fix (sanity checks in pciback driver) by upgrading the driver domain Linux kernel to a version beyond 4.3, or apply vendor-specific patches. Alternatively, ensure untrusted guests cannot access PCI passthrough capabilities if patching is not immediately feasible.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation6.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,160
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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-2015-8551 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