CVE-2026-46192 Overview
CVE-2026-46192 affects the Linux kernel's Microchip core Quad Serial Peripheral Interface (QSPI) driver. The driver incorrectly attempts to transmit garbage data during emulated read-only dual or quad SPI operations. The QSPI controller core already generates the required clock cycles for reads, making driver-level transmission unnecessary and harmful. This behavior bricks transfers because QSPI lacks a dedicated master-out line equivalent to MOSI in standard SPI. The issue has been resolved through upstream Linux kernel commits.
Critical Impact
Affected systems using the microchip-core-qspi driver experience failed dual or quad read transfers, disrupting flash memory access and dependent boot or runtime operations.
Affected Products
- Linux kernel builds including the spi-microchip-core-qspi driver
- Microchip PolarFire SoC and related platforms using the core QSPI controller
- Embedded Linux distributions shipping the unpatched driver
Discovery Timeline
- 2026-05-28 - CVE-2026-46192 published to NVD
- 2026-05-28 - Last updated in NVD database
Technical Details for CVE-2026-46192
Vulnerability Analysis
The microchip-core-qspi driver implements emulated dual and quad read operations on the Microchip QSPI controller. During these read-only transfers, the driver previously pushed garbage bytes onto the bus to force the controller to generate clock cycles. However, the QSPI core already produces the necessary clock pulses for read phases without driver intervention. The redundant transmission attempt bricks the transfer entirely.
Unlike standard SPI, QSPI multiplexes its data lines and lacks a dedicated master-out signal such as MOSI. Transmitting data while the controller expects to receive disrupts the bus state. The maintainers note uncertainty about whether the garbage bytes themselves corrupt the bus or whether the controller loses its internal direction tracking. Either way, the transfer fails to complete.
Root Cause
The root cause is a logic flaw in the driver's handling of read-only dual and quad operations. The code path generates write activity when only clock generation by the core is needed. This stems from a misunderstanding of the QSPI controller's behavior compared to traditional SPI hardware. The result is a functional bug that manifests as transfer failure rather than a security boundary violation in the classical sense.
Attack Vector
This flaw is a kernel driver reliability issue rather than a remote attack vector. Exploitation requires the system to execute dual or quad read operations through the affected driver. The impact is denial of service against the QSPI peripheral, which typically connects to flash memory. Systems relying on QSPI flash for runtime data access or boot operations may fail to function correctly. No network attack path is associated with this entry.
The vulnerability manifests at the driver level during specific transfer modes. See the referenced kernel commits for the precise code paths involved.
Detection Methods for CVE-2026-46192
Indicators of Compromise
- Kernel log messages indicating failed or stalled SPI transfers on the microchip-core-qspi device
- QSPI flash read errors during boot or runtime on Microchip SoC platforms
- Applications dependent on QSPI-backed storage reporting I/O failures
Detection Strategies
- Audit running kernel versions on Microchip QSPI platforms against the patched commits 67184f3, eb56dea, and ec9d0dd
- Inspect dmesg output for repeated spi-microchip-core-qspi transfer errors during dual or quad read operations
- Validate flash read integrity using checksums after firmware updates or boot sequences
Monitoring Recommendations
- Track kernel package versions across embedded Linux fleets to confirm patch deployment
- Forward kernel ring buffer logs to a central logging platform for trend analysis of SPI subsystem failures
- Monitor device boot success rates and flash access latency on affected hardware platforms
How to Mitigate CVE-2026-46192
Immediate Actions Required
- Identify all Linux systems running the microchip-core-qspi driver, particularly Microchip PolarFire SoC deployments
- Apply the upstream kernel patches referenced in commits 67184f3, eb56dea, and ec9d0dd
- Rebuild and redeploy kernel images for embedded targets that include the fix
Patch Information
The fix removes the garbage-data transmission during emulated read-only dual and quad operations. The patched driver allows the QSPI core to generate clock cycles natively without driver-side write activity. Refer to the Kernel Git Commit 67184f3, Kernel Git Commit eb56dea, and Kernel Git Commit ec9d0dd for the upstream changes.
Workarounds
- Avoid dual or quad read modes on affected hardware until the patched kernel is deployed
- Configure QSPI flash drivers to operate in standard single-line SPI mode where supported
- Pin embedded device firmware to kernel builds that include the upstream fix
# Verify the running kernel version on the affected system
uname -r
# Check whether the microchip-core-qspi driver is loaded
lsmod | grep microchip_core_qspi
# Review SPI subsystem messages for transfer errors
dmesg | grep -i "microchip-core-qspi"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
