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CVE Record

CVE-2020-25601: An issue was discovered in Xen through 4.14.x.

An issue was discovered in Xen through 4.14.x. There is a lack of preemption in evtchn_reset() / evtchn_destroy(). In particular, the FIFO event channel model allows guests to have a large number of event channels active at a time. Closing all of these (when resetting all event channels or when cleaning up after the guest) may take extended periods of time. So far, there was no arrangement for preemption at suitable intervals, allowing a CPU to spend an almost unbounded amount of time in the processing of these operations. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. All Xen versions are vulnerable in principle. Whether versions 4.3 and older are vulnerable depends on underlying hardware characteristics.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This Xen issue lets a malicious or faulty guest consume excessive CPU time during event-channel cleanup. The practical business risk is host-level denial of service: workloads sharing the affected Xen system could become unavailable or unstable.

Executive priority

Treat this as a high-priority availability risk for Xen virtualization platforms, especially shared infrastructure. It is not described as data theft or code execution, but a guest-triggered host denial of service can still cause material outage impact.

Technical view

CVE-2020-25601 is a lack of preemption in Xen evtchn_reset() and evtchn_destroy(). FIFO event channels can leave many active channels to close, allowing cleanup to run for an extended, nearly unbounded period and affect the whole system.

Likely exposure

Exposure is most relevant to organizations running Xen hypervisors, especially multi-tenant or untrusted-guest environments. The bundle says all Xen versions are vulnerable in principle, including Xen through 4.14.x.

Exploitation context

The source bundle does not show KEV listing or active exploitation evidence. It states that malicious or buggy guest kernels can mount a denial-of-service attack affecting the entire system.

Researcher notes

Key uncertainty is product-version precision: the bundle says all Xen versions are vulnerable in principle, while Xen 4.3 and older depend on hardware characteristics. No CVSS, CWE, or confirmed exploitation source is provided.

Mitigation direction

  • Review Xen XSA-344 and applicable distribution advisories for fixed Xen packages.
  • Update Xen hypervisors using vendor-supported packages or patches.
  • Prioritize hosts running untrusted, customer-controlled, or high-risk guest kernels.
  • Limit guest administrative control where operationally feasible until remediation is complete.
  • Monitor hypervisors for abnormal CPU stalls or guest cleanup-related availability issues.

Validation and detection

  • Inventory Xen hypervisors and record installed Xen versions.
  • Identify hosts running Xen through 4.14.x or older Xen branches.
  • Check whether vendor packages include the XSA-344 fix.
  • Confirm all affected hypervisors are updated after maintenance windows.
  • Review virtualization logs for guest-triggered cleanup or reset anomalies.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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