Debian LinuxOperating system · Debian
CVE-2018-7540
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 through 4.10.x allowing x86 PV guest OS users to cause a denial of service (host OS CPU hang) via non-preemptable L3/L4 pagetable freeing.
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 through 4.10.x, x86 PV (paravirtualized) guest OS users can trigger non-preemptable L3/L4 pagetable freeing, causing the host CPU to hang and resulting in a denial of service condition. The vulnerability exists in the hypervisor's page table management for PV guests.
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<= 4.10.0CVSS 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.
-
Identify Xen hypervisor versionRun 'xl info' or 'xm info' to display Xen hypervisor information, or check the package version with 'dpkg -l | grep xen' on Debian or 'rpm -q xen' on RHEL-based systemsAffected if The displayed Xen version is 4.10.0 or earlier
-
Verify running hypervisor is XenCheck /sys/hypervisor/ for Xen-specific files, or run 'cat /proc/xen/capabilities' which should exist on a Xen hostAffected if The system is running Xen as the hypervisor and the version is <= 4.10.0
-
Check for active PV guestsRun 'xl list' or 'virsh list --all' to list all running and defined virtual machines; look for guests that are paravirtualized (PV) rather than fully virtualized (HVM)Affected if Any x86 PV guest is running or configured on the affected Xen version
-
Inspect guest configuration typeExamine guest configuration files in /etc/xen/ or via 'xl cfglist <guestname>' to determine if guests are configured as 'paravirt' or have PV drivers enabledAffected if Guests are configured with paravirtualization (pvgrub, pygrub, or PV drivers) on Xen <= 4.10.0
A system is affected if it runs Xen version 4.10.0 or earlier with x86 PV (paravirtualized) guest support enabled, as the vulnerability lies in the hypervisor's page table management for PV guests.
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 Xen security patches or upgrade to a version beyond 4.10.x. If immediate patching is not possible, consider disabling PV guest support or ensuring only trusted tenants have PV guest access.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-7540 — 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-2018-7540 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
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.
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
- No spam, self-promotion, credentials, or personal data