Advisory [CVE-2026-64086] (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer
This security 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: not rated.
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 is not a statement that 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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