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CVE Record

CVE-2021-4441: spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op()

In the Linux kernel, the following vulnerability has been resolved: spi: spi-zynq-qspi: Fix a NULL pointer dereference in zynq_qspi_exec_mem_op() In zynq_qspi_exec_mem_op(), kzalloc() is directly used in memset(), which could lead to a NULL pointer dereference on failure of kzalloc(). Fix this bug by adding a check of tmpbuf. This bug was found by a static analyzer. The analysis employs differential checking to identify inconsistent security operations (e.g., checks or kfrees) between two code paths and confirms that the inconsistent operations are not recovered in the current function or the callers, so they constitute bugs. Note that, as a bug found by static analysis, it can be a false positive or hard to trigger. Multiple researchers have cross-reviewed the bug. Builds with CONFIG_SPI_ZYNQ_QSPI=m show no new warnings, and our static analyzer no longer warns about this code.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-4441 is a Linux kernel bug in the Zynq QSPI SPI driver. If memory allocation fails, the driver could dereference a null pointer and crash that code path. The source notes this was found by static analysis and may be hard to trigger.

Executive priority

Treat as a targeted kernel reliability risk, not an internet-scale emergency based on current evidence. Prioritize patch verification for embedded Zynq deployments and managed appliances using vendor kernels.

Technical view

The issue is in zynq_qspi_exec_mem_op(), where kzalloc() output was passed into memset() without checking for allocation failure. Kernel stable fixes add a tmpbuf null check. The affected evidence points to Linux kernel versions around 5.2 through 5.17-era stable lines, but downstream backports must be verified.

Likely exposure

Exposure is most likely on Linux systems using the Xilinx Zynq QSPI driver, especially embedded or SoC platforms with CONFIG_SPI_ZYNQ_QSPI enabled or loaded. General Linux servers without this driver path are less likely exposed.

Exploitation context

No CISA KEV listing or source-bundle evidence indicates active exploitation. The CVE text says the bug was found by static analysis, may be a false positive or hard to trigger, and was cross-reviewed by researchers.

Researcher notes

The fix addresses missing error handling after kzalloc() in zynq_qspi_exec_mem_op(). The source bundle provides no CVSS, CWE, crash trace, proof of exploitation, or complete downstream product matrix, so exposure assessment depends on kernel configuration and vendor backports.

Mitigation direction

  • Update to a kernel or vendor package containing the referenced stable fix.
  • For vendor kernels, confirm the tmpbuf null-check patch was backported.
  • Prioritize embedded Zynq systems using the QSPI driver.
  • Check Linux distribution and device vendor advisories for supported updates.

Validation and detection

  • Inventory systems running Linux kernels in the affected version range.
  • Check whether CONFIG_SPI_ZYNQ_QSPI is enabled as built-in or module.
  • Verify installed kernel source includes the tmpbuf allocation failure check.
  • Confirm device vendor kernels include one of the stable fix commits.
Prepared
Confidence
medium
Sources
7

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-2021-4441 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
1ADP providers
6Source 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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux67dca5e580f1e93a66177389981541cac208c817, 67dca5e580f1e93a66177389981541cac208c817, 67dca5e580f1e93a66177389981541cac208c817, 67dca5e580f1e93a66177389981541cac208c817, 67dca5e580f1e93a66177389981541cac208c817unaffected
LinuxLinux5.2, 0, 5.4.182, 5.10.103, 5.15.26, 5.16.12, 5.17affected
Weakness

CWE details

No CWE listed

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