CVE-2026-46007 Overview
CVE-2026-46007 is a Linux kernel vulnerability in the hwmon subsystem, specifically the powerz driver. The transfer buffer used for Direct Memory Access (DMA) operations may share a cacheline with a following mutex structure, depending on the underlying CPU architecture. This memory layout creates a coherency hazard when DMA operations execute concurrently with mutex manipulation. The kernel maintainers resolved the issue by switching to high-level DMA helpers that guarantee proper buffer alignment and prevent cacheline sharing.
Critical Impact
DMA operations on the powerz hwmon transfer buffer can corrupt adjacent mutex state through cacheline sharing, leading to potential memory corruption or undefined kernel behavior on affected architectures.
Affected Products
- Linux kernel hwmon subsystem - powerz driver
- Architectures where DMA buffers and adjacent mutex structures can occupy the same cacheline
- Stable kernel branches referenced by upstream commits 1869da3e, 270e5c57, 2fa22730, and 3023c050
Discovery Timeline
- 2026-05-27 - CVE-2026-46007 published to NVD
- 2026-05-27 - Last updated in NVD database
Technical Details for CVE-2026-46007
Vulnerability Analysis
The powerz driver in the Linux kernel hwmon subsystem allocates a transfer buffer used for USB DMA communication with ChargerLAB POWER-Z power monitoring hardware. The driver structure places this transfer buffer adjacent to a mutex used to serialize device access. On architectures with cacheline sizes large enough to encompass both fields, the DMA buffer and mutex share a single cacheline.
Cacheline sharing between DMA memory and CPU-manipulated structures violates the DMA API contract. When a device writes into the DMA buffer, the cacheline must be invalidated. When the CPU concurrently modifies the adjacent mutex, the same cacheline is written back. These overlapping operations create a race that can corrupt either the DMA payload or the mutex internals.
The upstream fix replaces the manual buffer placement with high-level DMA helpers. These helpers allocate the buffer separately with appropriate alignment guarantees, ensuring the DMA region cannot share a cacheline with adjacent kernel data structures.
Root Cause
The root cause is improper DMA buffer placement within a driver structure. The transfer buffer was declared inline next to a mutex without alignment padding, allowing them to occupy the same cacheline on architectures with sufficiently large cacheline granularity. This is a kernel driver memory layout flaw that violates DMA coherency requirements.
Attack Vector
The vulnerability requires the powerz driver to be loaded and a compatible POWER-Z USB device to be connected. Triggering the condition depends on concurrent DMA traffic and mutex contention. The flaw is a memory safety issue arising from hardware interaction rather than a network-exploitable bug, and no exploit code is publicly available.
The issue manifests in the boundary between the DMA buffer and the adjacent mutex field within the driver's private data structure. See the kernel commit references for the precise structure layout changes that resolve the cacheline sharing.
Detection Methods for CVE-2026-46007
Indicators of Compromise
- Unexpected kernel warnings or oops messages referencing the powerz driver in dmesg output
- Mutex corruption traces or lockdep splats originating from hwmon driver code paths
- USB device communication failures with ChargerLAB POWER-Z hardware on patched-but-not-rebooted systems
Detection Strategies
- Audit running kernel versions against the fixed commits 1869da3efe70, 270e5c576a6e, 2fa2273016a0, and 3023c050af36 to identify unpatched hosts
- Monitor kernel logs for powerz module load events on systems where the driver is not required, indicating unnecessary attack surface
- Inspect kernel build configurations to determine whether CONFIG_SENSORS_POWERZ is enabled in deployed images
Monitoring Recommendations
- Enable kernel lockdep and KASAN in test environments to surface memory and locking anomalies in hwmon drivers
- Collect kernel crash dumps from production systems to identify recurring faults associated with hwmon subsystem activity
- Track upstream stable kernel releases and align patch deployment cadence with vendor advisories
How to Mitigate CVE-2026-46007
Immediate Actions Required
- Apply the upstream stable kernel patches referenced in the Kernel Git Commit 1869da3e, Commit 270e5c57, Commit 2fa22730, and Commit 3023c050
- Reboot affected systems into the patched kernel to load the corrected powerz driver
- Inventory systems with the powerz module loaded using lsmod | grep powerz to scope remediation
Patch Information
The fix is upstream in the Linux kernel hwmon subsystem. The patch replaces inline DMA buffer placement with high-level DMA allocation helpers that enforce alignment. Distributions tracking stable kernel branches should pull the referenced commits into their next security update. Verify the installed kernel version using uname -r and compare against vendor changelogs.
Workarounds
- Blacklist the powerz module on systems that do not require ChargerLAB POWER-Z monitoring by adding blacklist powerz to /etc/modprobe.d/blacklist.conf
- Unload the running module with modprobe -r powerz where the driver is currently loaded and not in active use
- Restrict physical USB access to prevent attachment of POWER-Z hardware on systems where the driver is built but not blacklisted
# Configuration example
echo 'blacklist powerz' | sudo tee /etc/modprobe.d/disable-powerz.conf
sudo modprobe -r powerz
sudo update-initramfs -u
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
