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CVE Record

CVE-2025-39921: spi: microchip-core-qspi: stop checking viability of op->max_freq in supports_op callback

In the Linux kernel, the following vulnerability has been resolved: spi: microchip-core-qspi: stop checking viability of op->max_freq in supports_op callback In commit 13529647743d9 ("spi: microchip-core-qspi: Support per spi-mem operation frequency switches") the logic for checking the viability of op->max_freq in mchp_coreqspi_setup_clock() was copied into mchp_coreqspi_supports_op(). Unfortunately, op->max_freq is not valid when this function is called during probe but is instead zero. Accordingly, baud_rate_val is calculated to be INT_MAX due to division by zero, causing probe of the attached memory device to fail. Seemingly spi-microchip-core-qspi was the only driver that had such a modification made to its supports_op callback when the per_op_freq capability was added, so just remove it to restore prior functionality.

MediumCVSS 5.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel availability bug affecting systems that use the Microchip Core QSPI SPI memory driver. During device probing, the driver can reject attached memory because it evaluates an invalid zero frequency value. The practical impact is failed memory-device initialization, not data theft or privilege escalation based on the supplied sources.

Executive priority

Treat as a targeted availability risk for affected Linux-based appliances or embedded systems. It is not currently evidenced as internet-exploited or confidentiality-impacting, but affected devices may fail critical storage initialization and should be updated through normal kernel maintenance.

Technical view

The microchip-core-qspi driver copied max_freq validation into supports_op. During probe, op->max_freq is zero, leading to an invalid baud-rate calculation and failed attached memory probing. The kernel fix removes that supports_op check, restoring prior behavior. CVSS is 5.5 with local, low-privilege availability impact.

Likely exposure

Exposure is likely limited to Linux systems using the Microchip Core QSPI driver with attached SPI memory. The CVE data lists Linux kernel versions including 6.14, 6.16.6, and 6.17 as affected, but distribution-specific backports require vendor verification.

Exploitation context

The CVE is not in KEV, and the supplied sources do not report active exploitation. The described impact is operational availability: memory-device probe failure. CVSS indicates local access with low privileges, no user interaction, and high availability impact.

Researcher notes

The key behavior is probe-time invalidity of op->max_freq. The vulnerability appears to be a regression from per-operation frequency support. Avoid assuming a generic Linux-wide outage; confirm the specific driver, hardware dependency, and vendor backport state.

Mitigation direction

  • Apply Linux distribution kernel updates containing the referenced stable fixes.
  • Check vendor kernel advisories for backported fixes and affected package names.
  • Prioritize devices relying on Microchip Core QSPI attached memory.
  • If no update is available, follow vendor guidance for temporary workarounds.

Validation and detection

  • Inventory systems using the microchip-core-qspi Linux kernel driver.
  • Map running kernel builds to vendor advisories and the referenced stable commits.
  • Review boot or kernel logs for attached SPI memory probe failures.
  • Confirm updated kernels include the fix removing max_freq checks from supports_op.
Prepared
Confidence
high
Sources
4

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-2025-39921 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
1ADP providers
3Source 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-2025-39921Attack 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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux13529647743d906ed3cf991f1d77727e7ff1fb6f, 13529647743d906ed3cf991f1d77727e7ff1fb6funaffected
LinuxLinux6.14, 0, 6.16.6, 6.17affected
Weakness

CWE details

No CWE listed

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