Debian LinuxOperating system · Debian
CVE-2020-15566
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 4.13.x, allowing guest OS users to cause a host OS crash because of incorrect error handling in event-channel port allocation. The allocation of an event-channel port may fail for multiple reasons: (1) port is already in use, (2) the memory allocation failed, or (3) the port we try to allocate is higher than what is supported by the ABI (e.g., 2L or FIFO) used by the guest or the limit set by an administrator (max_event_channels in xl cfg). Due to the missing error checks, only (1) will be considered an error. All the other cases will provide a valid port and will result in a crash when trying to access the event channel. When the administrator configured a guest to allow more than 1023 event channels, that guest may be able to crash the host. When Xen is out-of-memory, allocation of new event channels will result in crashing the host rather than reporting an error. Xen versions 4.10 and later are affected. All architectures are affected. The default configuration, when guests are created with xl/libxl, is not vulnerable, because of the default event-channel limit.
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 4.13.x, the event-channel port allocation logic lacks proper error handling for failures other than 'port already in use.' When memory allocation fails or the requested port exceeds ABI or administrator limits (max_event_channels), the code returns an invalid port instead of reporting an error, causing a host crash when the guest attempts to use the event channel. Guests configured with more than 1023 event channels can trigger this condition, and memory exhaustion makes the host vulnerable.
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
= 10.0>= 4.10.0, <= 4.13.1CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check Xen hypervisor versionRun 'xl version' or 'xm version' to determine the installed Xen version, or check the package version with 'dpkg -l | grep xen' on DebianAffected if Version is between 4.10.0 and 4.13.1 inclusive (including 4.13.x before the fix)
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Identify guest configurations with high event channel limitsFor each guest domain, inspect the configuration file (typically in /etc/xen/ or /var/lib/xen/auto/) and look for the 'max_event_channels' settingAffected if Any guest configuration has max_event_channels set to a value greater than 1023
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List running guests with elevated event channel allocationsRun 'xl list -l <domain>' for each active guest and check the 'max_event_channels' value in the output, or use 'xl dominfo <domain>'Affected if Any active guest has an event channel allocation exceeding 1023 ports
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Assess host memory pressure conditionsMonitor available memory with 'free -h' or check for OOM killer activity in 'dmesg' logs, especially relevant if guests are actively using high event channel countsAffected if Host memory is exhausted or near exhaustion while guests request event channel allocations
The environment is affected if the Xen version is between 4.10.0 and 4.13.1 AND any guest is configured with or actively using more than 1023 event channels, particularly under memory pressure conditions.
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 dataEnsure guest configurations do not set max_event_channels above 1023, or upgrade Xen to a patched version that properly handles event-channel allocation errors.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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 locallyCheck whether your project pulls in CVE-2020-15566 — 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-2020-15566 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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- Version or environment caveats, and links to real fixes
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