Medium [CVE-2026-64086] (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer
This medium-severity Red Hat Linux advisory covers CVE-2026-64086.
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Summary
In the Linux kernel, the following vulnerability has been resolved: hwmon: (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer adm1266_pmbus_block_xfer() sets up the read transaction with.buf = data->read_buf,.len = ADM1266_PMBUS_BLOCK_MAX + 2, but read_buf in struct adm1266_data is declared as u8 read_buf[ADM1266_PMBUS_BLOCK_MAX + 1]; For a max-length block response (length byte = 255 + up to 1 PEC byte), the i2c controller is told to write 257 bytes into a 256-byte buffer, putting one byte past the end of read_buf.
The same response also makes the subsequent PEC compare if (crc!= msgs[1].buf[msgs[1].buf[0] + 1]) read a byte beyond the array. Bump the read_buf declaration to ADM1266_PMBUS_BLOCK_MAX + 2 so the buffer can hold the length byte, up to 255 payload bytes, and the PEC byte the i2c_msg length already accounts for.
A flaw was found in the Linux kernel's hwmon (hardware monitoring) subsystem, specifically in the pmbus/adm1266 driver. The `adm1266_pmbus_block_xfer()` function attempts to read one byte more than the allocated buffer size during a block transfer read operation.
This out-of-bounds write can lead to memory corruption and potentially an information disclosure or denial of service. Red Hat severity: Moderate.
Weakness: CWE-787.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
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