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CVE Record

CVE-2021-47439: net: dsa: microchip: Added the condition for scheduling ksz_mib_read_work

In the Linux kernel, the following vulnerability has been resolved: net: dsa: microchip: Added the condition for scheduling ksz_mib_read_work When the ksz module is installed and removed using rmmod, kernel crashes with null pointer dereferrence error. During rmmod, ksz_switch_remove function tries to cancel the mib_read_workqueue using cancel_delayed_work_sync routine and unregister switch from dsa. During dsa_unregister_switch it calls ksz_mac_link_down, which in turn reschedules the workqueue since mib_interval is non-zero. Due to which queue executed after mib_interval and it tries to access dp->slave. But the slave is unregistered in the ksz_switch_remove function. Hence kernel crashes. To avoid this crash, before canceling the workqueue, resetted the mib_interval to 0. v1 -> v2: -Removed the if condition in ksz_mib_read_work

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A Linux kernel driver for Microchip KSZ network switches can crash the kernel when the module is removed. This is mainly an availability risk for systems that use this hardware or driver, especially embedded or network devices. The provided sources do not show remote exploitation or active exploitation.

Executive priority

Prioritize patching where KSZ-based network or embedded devices support critical operations. This is not evidenced as internet-exploitable, but a local-triggered kernel crash can still disrupt availability.

Technical view

The KSZ DSA driver can reschedule ksz_mib_read_work during switch unregister because mib_interval remains nonzero. After ksz_switch_remove unregisters the slave interface, the delayed work may still run and dereference dp->slave, causing a kernel null pointer crash. The upstream fix resets mib_interval to zero before canceling the workqueue.

Likely exposure

Exposure is likely limited to Linux systems running affected kernel builds with the Microchip KSZ DSA switch driver in use. The CVSS vector is local, low complexity, low privilege, no user interaction, with high availability impact.

Exploitation context

The source describes crashes during ksz module removal using rmmod. KEV is false, and the bundle provides no evidence of active exploitation, public exploitation, or remote attack paths.

Researcher notes

The evidence points to a teardown ordering bug in the KSZ DSA driver workqueue handling. Affected-version data in the bundle is limited, so validate exposure against actual kernel source, distro patches, and device-vendor kernels.

Mitigation direction

  • Update to a kernel or vendor package containing the referenced stable fixes.
  • Check Linux distribution or device-vendor guidance for backported patches.
  • Avoid unnecessary KSZ module unload or reload operations until patched.
  • Restrict local access and module-management permissions on affected systems.

Validation and detection

  • Inventory systems for affected Linux kernel versions and Microchip KSZ DSA driver usage.
  • Confirm whether the referenced stable commits or vendor backports are present.
  • Review kernel logs for null pointer crashes during KSZ module removal or switch teardown.
  • Verify operational runbooks do not unload the KSZ module on unpatched systems.
Prepared
Confidence
high
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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CVE-2021-47439 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
5.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

1CVSS vectors
3Timeline events
2ADP providers
4Source links

SSVC decision data

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

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

5.5Medium
CVSS 3.1 vector shape for CVE-2021-47439Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux469b390e1ba330e888175e55d78573db2e9a8cb4, 469b390e1ba330e888175e55d78573db2e9a8cb4, 469b390e1ba330e888175e55d78573db2e9a8cb4unaffected
LinuxLinux5.7, 0, 5.10.75, 5.14.14, 5.15affected
Weakness

CWE details

No CWE listed

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