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CVE Record

CVE-2021-47061: KVM: Destroy I/O bus devices on unregister failure _after_ sync'ing SRCU

In the Linux kernel, the following vulnerability has been resolved: KVM: Destroy I/O bus devices on unregister failure _after_ sync'ing SRCU If allocating a new instance of an I/O bus fails when unregistering a device, wait to destroy the device until after all readers are guaranteed to see the new null bus. Destroying devices before the bus is nullified could lead to use-after-free since readers expect the devices on their reference of the bus to remain valid.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel KVM memory-safety flaw. Under a failed device-unregister path, KVM could destroy an I/O bus device before all readers stop using it, creating a possible use-after-free. Business risk is concentrated on systems running affected Linux kernels with KVM virtualization enabled.

Executive priority

Treat this as a virtualization platform hygiene issue, not an internet-wide emergency. Prioritize KVM hosts and cloud or hosting infrastructure, but urgency is constrained by missing severity, exploitability, and vendor-specific exposure evidence.

Technical view

The bug is in KVM I/O bus unregister handling. If allocation of a replacement bus fails, device destruction could occur before SRCU readers are synchronized and before readers observe the null bus, violating KVM reader lifetime assumptions and risking use-after-free.

Likely exposure

Exposure appears limited to Linux systems using KVM on affected kernel versions or unfixed downstream builds. The source lists Linux as affected and references stable kernel fixes, but provides no CPEs, CVSS score, or distribution-specific package mapping.

Exploitation context

The provided sources do not report active exploitation, public exploit tooling, or KEV listing. The impact mechanism is a kernel use-after-free, but practical exploitability and attacker prerequisites are not established in the source bundle.

Researcher notes

Key unresolved details are attacker prerequisites, reachable trigger paths, and downstream affected ranges. The source establishes the race/lifetime bug and fix direction, but not exploitability, CVSS, CWE, or distribution package status.

Mitigation direction

  • Prioritize inventory of Linux virtualization hosts using KVM.
  • Check OS vendor advisories for kernels containing the referenced stable fixes.
  • Upgrade affected kernels through supported distribution update channels.
  • Apply compensating controls around KVM hosts until vendor guidance is confirmed.

Validation and detection

  • Identify running kernel versions on KVM-enabled hosts.
  • Confirm whether downstream kernel packages include the referenced fixes.
  • Review virtualization hosts for KVM module usage and guest workload exposure.
  • Track CVE-2021-47061 status in vendor security advisories.
Prepared
Confidence
medium
Sources
6

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47061 mapping review

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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
3Timeline events
2ADP providers
5Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf65886606c2d3b562716de030706dfe1bea4ed5e, f65886606c2d3b562716de030706dfe1bea4ed5e, f65886606c2d3b562716de030706dfe1bea4ed5e, f65886606c2d3b562716de030706dfe1bea4ed5e, f0dfffce3f4ffd5f822568a4a6fb34c010e939d1, 840e124f89a5127e7eb97ebf377f4b8ca745c070, 40a023f681befd9b2862a3c16fb306a38b359ae5, 19184bd06f488af62924ff1747614a8cb284ad63, 41b2ea7a6a11e2b1a7f2c29e1675a709a6b2b98d, 68c125324b5e1d1d22805653735442923d896a1dunaffected
LinuxLinux5.9, 0, 5.10.37, 5.11.21, 5.12.4, 5.13affected
Weakness

CWE details

No CWE listed

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