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CVE Record

CVE-2021-47361: mcb: fix error handling in mcb_alloc_bus()

In the Linux kernel, the following vulnerability has been resolved: mcb: fix error handling in mcb_alloc_bus() There are two bugs: 1) If ida_simple_get() fails then this code calls put_device(carrier) but we haven't yet called get_device(carrier) and probably that leads to a use after free. 2) After device_initialize() then we need to use put_device() to release the bus. This will free the internal resources tied to the device and call mcb_free_bus() which will free the rest.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47361 is a Linux kernel flaw in error handling for the MCB bus allocation path. The issue may cause incorrect device reference cleanup and a possible use-after-free in specific failure conditions. The supplied sources do not define an attack vector, business impact, or active exploitation.

Executive priority

Treat as a kernel hygiene item unless local context shows MCB usage on sensitive systems. There is no supplied evidence of exploitation or broad remote exposure, but kernel memory-safety bugs should be remediated through normal patch cycles.

Technical view

The kernel fix addresses two mcb_alloc_bus() cleanup bugs: calling put_device(carrier) before get_device(carrier) if ida_simple_get() fails, and failing to use put_device() after device_initialize() to release bus resources through mcb_free_bus(). The record lists affected Linux kernel versions and multiple stable fix commits.

Likely exposure

Exposure appears limited to Linux systems running affected kernel versions where the MCB subsystem and mcb_alloc_bus() path are present. The source bundle does not identify affected distributions, default configurations, remote reachability, or required privileges.

Exploitation context

The supplied sources do not show KEV listing, active exploitation, public exploit use, or a proof of concept. The bug is described as an error-path memory lifecycle issue, but triggering conditions and security impact are not fully documented in the bundle.

Researcher notes

Key uncertainty is impact. The record describes a possible use-after-free from reference-counting cleanup mistakes, but no CVSS, CWE, exploitability analysis, or privilege boundary is provided. Research should focus on reachable callers, kernel configuration, and vendor backport status.

Mitigation direction

  • Update affected Linux kernels using vendor-supported packages containing the stable fixes.
  • Check distribution advisories for CVE-2021-47361 or the referenced commit IDs.
  • Prioritize systems that load or depend on the Linux MCB subsystem.
  • Avoid unsupported kernel builds where stable fixes cannot be verified.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded systems.
  • Check whether kernel packages include the referenced stable commits or vendor backports.
  • Review running kernel configuration and modules for MCB subsystem presence.
  • Confirm vulnerability scanner findings against actual kernel build metadata.
Prepared
Confidence
medium
Sources
9

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.

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CVE-2021-47361 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
8Source 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

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63d, 18d28819809909c3f24bb72183a901c5e332a63dunaffected
LinuxLinux4.7, 0, 4.9.285, 4.14.249, 4.19.209, 5.4.150, 5.10.70, 5.14.9, 5.15affected
Weakness

CWE details

No CWE listed

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