Debian LinuxOperating system · Debian
CVE-2018-7542
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 · uneditedAn issue was discovered in Xen 4.8.x through 4.10.x allowing x86 PVH guest OS users to cause a denial of service (NULL pointer dereference and hypervisor crash) by leveraging the mishandling of configurations that lack a Local APIC.
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 confidenceIn Xen 4.8.x through 4.10.x, the PVH (Paravirtualized Hardware) guest hypercall path fails to properly handle configurations lacking a Local APIC. When a PVH guest is configured without a Local APIC, the hypervisor attempts to dereference a NULL pointer, causing a hypervisor crash and resulting in a denial of service affecting the entire host.
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
= 9.0>= 4.8.0, <= 4.10.0CVSS 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:3.0/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 checksWork through these to decide whether this CVE applies to you.
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Check the installed Xen hypervisor versionRun `xl info` or `xm info` and look for the 'xen_version' field, or check the package version with `dpkg -l | grep xen-hypervisor` on DebianAffected if The version is 4.8.0 through 4.10.0 inclusive
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Identify PVH guest domainsRun `xl list` or `xm list` to list all guest domains. Look for guests with type 'pvh' in the output, or inspect guest configuration files in /etc/xen/ for `pvh=1` or `pvh=0` settingsAffected if Any PVH guests (Paravirtualized Hardware) are defined in the environment
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Check if Local APIC is available to PVH guestsInspect the PVH guest configuration file and check for APIC-related settings such as `apic=0`, `noapic`, or the absence of ACPI/MP table configuration that would provide a Local APIC to the guestAffected if A PVH guest is configured with no Local APIC (apic=0 or noapic) or lacks ACPI tables that would expose a Local APIC
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Verify the host hardware supports and exposes Local APICRun `xl cpupool-list` or check BIOS settings to confirm the physical hardware has a working Local APIC that could be passed to or used by guestsAffected if The host hardware lacks a functioning Local APIC and PVH guests are configured without one explicitly
A system is affected if it runs Xen 4.8.0-4.10.0 with any PVH guest configured to operate without a Local APIC, which will trigger a hypervisor crash on hypercall invocation.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the appropriate Xen security patch to address the NULL pointer dereference. Ensure PVH guest configurations are reviewed and tested, particularly any that may operate without a Local APIC.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation4.0 h
- Implementation2.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-7542 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-7542 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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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.
- 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
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