CVE-2026-64087 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (pmbus/adm1266) reject implausible blackbox record_count
adm1266_nvmem_read_blackbox() loops over a record_count that comes straight from byte 3 of the BLACKBOX_INFO response. The destination buffer is data->dev_mem, sized for the nvmem cell's declared 2048 bytes (ADM1266_BLACKBOX_MAX_RECORDS * ADM1266_BLACKBOX_SIZE = 32 * 64). A device that reports a record_count greater than 32 -- whether due to firmware bugs, bus corruption, or a non-responsive slave returning 0xff -- would walk read_buff past the end of the dev_mem allocation on the trailing iterations.
Cap record_count at ADM1266_BLACKBOX_MAX_RECORDS (introduced here) before entering the loop and return -EIO on any larger value, so a malformed BLACKBOX_INFO response cannot drive the loop out of bounds.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability in question affects the Linux kernel's hardware monitoring subsystem, specifically within the pmbus/adm1266 driver implementation. This issue arises from an insufficient validation mechanism that processes blackbox record counts obtained directly from hardware responses without proper bounds checking. The flaw exists in the adm1266_nvmem_read_blackbox() function which handles data retrieval from the ADM1266 power management unit device. When a device responds with a BLACKBOX_INFO command, it returns a record_count value in byte 3 that determines how many iterations the reading loop will execute.
The technical implementation flaw stems from the lack of input validation on the record_count parameter obtained from hardware communication. The driver allocates a fixed-size buffer of 2048 bytes specifically designed to hold up to 32 records of 64 bytes each, as defined by ADM1266_BLACKBOX_MAX_RECORDS and ADM1266_BLACKBOX_SIZE constants. However, the function fails to validate whether the received record_count value exceeds this predetermined maximum, creating a potential buffer overflow scenario. When an attacker or faulty hardware returns a record_count value greater than 32, the loop continues executing beyond the allocated memory boundaries.
This vulnerability represents a classic buffer over-read condition that can lead to memory corruption and potential privilege escalation opportunities within the kernel space. The operational impact extends beyond simple data corruption as it could enable malicious actors to exploit the out-of-bounds memory access for arbitrary code execution or system instability. The attack surface includes scenarios where firmware bugs, bus corruption, or non-responsive slave devices might return invalid record_count values of 0xff or other unexpected data. According to CWE classification, this maps directly to CWE-129: Improper Validation of Array Index, while the ATT&CK framework would categorize this under privilege escalation techniques through kernel memory corruption.
The mitigation strategy implemented in the fix involves enforcing strict bounds checking on the record_count value before entering the processing loop. The solution introduces a cap at ADM1266_BLACKBOX_MAX_RECORDS value, ensuring that any attempt to exceed the 32-record limit results in immediate termination with -EIO error code. This defensive programming approach prevents the out-of-bounds memory access by rejecting malformed responses at the point of entry rather than allowing the invalid data to propagate through the system. The fix aligns with security best practices for input validation and demonstrates proper bounds checking implementation that protects against buffer over-read conditions in kernel-level hardware drivers.