CVE-2026-63965 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
iio: pressure: bmp280: fix stack leak in bmp580 trigger handler
bmp580_trigger_handler() declares its scan buffer on the stack without an initializer and then memcpy()s 3 bytes of 24-bit sensor data into each 4-byte __le32 field. The high byte of comp_temp and comp_press is left uninitialized, and the channel storagebits is 32, so two bytes of stack are pushed to userspace per scan.
This is a regression from when the buffer lived in the private data, the move to a stack-local struct dropped the implicit zeroing. bme280_trigger_handler() was fixed up to handle this bug, but this driver was not fixed because there was no padding hole, but rather a short-fill issue.
Fix this all by just zero-initializing the structure on the stack.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability identified in the Linux kernel's iio pressure subsystem affects the bmp280 driver implementation specifically when handling bmp580 sensor triggers. This represents a stack-based information disclosure flaw that occurs during the processing of sensor data through the trigger handler mechanism. The issue stems from improper memory initialization within the bmp580_trigger_handler() function where a local scan buffer is declared on the stack without explicit zero-initialization. When the driver processes 24-bit sensor data, it uses memcpy() operations to transfer three bytes of data into each 4-byte __le32 field of the buffer structure.
The technical flaw manifests as a memory corruption pattern where the high byte portions of comp_temp and comp_press variables remain uninitialized after the memory copy operations. This occurs because the channel storage bits are set to 32 bits while the actual sensor data only occupies 24 bits, creating a scenario where two bytes of uninitialised stack memory get inadvertently exposed to userspace applications. The vulnerability represents a classic case of improper stack buffer initialization that can lead to information leakage from kernel memory regions.
This issue constitutes a regression from previous implementations where the scan buffer was stored within private driver data structures, which provided implicit zero-initialization through the allocation mechanism. The transition to stack-local storage removed this automatic initialization behavior, creating a security gap that allows sensitive kernel stack contents to be accessible through the sensor data interface. The problem is particularly concerning because it directly impacts the integrity of the IIO (Industrial I/O) subsystem's data handling mechanisms and exposes kernel memory to potential exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks that could leverage the leaked stack contents for privilege escalation or system compromise. Attackers could potentially harvest valuable kernel memory layout information, including addresses of kernel data structures, function pointers, or other sensitive metadata that might aid in bypassing security mitigations such as ASLR. This vulnerability affects systems using the bmp280 driver with bmp580 sensors and demonstrates how seemingly minor implementation changes can introduce significant security regressions.
The fix implemented addresses this issue through explicit zero-initialization of the stack-allocated structure, which ensures that all memory bytes within the buffer are properly initialized before data is copied into them. This approach aligns with secure coding practices recommended by industry standards such as CWE-121, which addresses stack-based buffer overflow vulnerabilities, and CWE-125, which covers out-of-bounds read conditions. The solution follows the principle of least privilege and memory safety by preventing information leakage through uninitialized memory contents.
Security practitioners should note that this vulnerability demonstrates how kernel driver implementations can introduce subtle security issues during refactoring or optimization efforts. The fix serves as a reminder of the importance of maintaining proper memory initialization practices, especially when transitioning between different memory allocation strategies within kernel subsystems. This case also highlights the necessity of thorough regression testing for security properties, particularly in drivers that handle sensor data where memory layout and initialization can have direct operational implications.
The vulnerability resolution through stack structure zero-initialization represents a defensive programming approach that aligns with the MITRE ATT&CK framework's concept of privilege escalation techniques involving information disclosure. By ensuring proper initialization, the fix prevents attackers from harvesting potentially useful information from kernel stack memory that could otherwise be used to aid in more sophisticated exploitation attempts. This remediation maintains the driver functionality while eliminating the security regression introduced by the stack-based buffer implementation change.
The fix demonstrates the importance of comprehensive testing across different code paths and data sizes when implementing sensor data handling mechanisms. The issue's resolution through explicit zero-initialization provides a robust solution that prevents similar vulnerabilities from manifesting in other parts of the IIO subsystem or related drivers, emphasizing the need for consistent secure coding practices throughout kernel development. This vulnerability serves as a practical example of how seemingly benign code changes can introduce security regressions requiring careful analysis and testing to identify and resolve effectively.