CVE-2026-64085

In the Linux kernel, the following vulnerability has been resolved:

hwmon: (pmbus/adm1266) bounce blackbox records through a protocol-sized buffer

adm1266_pmbus_block_xfer() copies the device-supplied block payload into the caller-provided buffer using the device-supplied length:

memcpy(data_r, &msgs[1].buf[1], msgs[1].buf[0]);

The helper does not know how large data_r is and trusts the device to return at most one records worth of bytes. adm1266_nvmem_read_blackbox() violates that contract: it advances read_buff inside data->dev_mem in ADM1266_BLACKBOX_SIZE (64-byte) strides while the helper is willing to write up to ADM1266_PMBUS_BLOCK_MAX (255) bytes. A device that returns more than 64 bytes on the trailing record (read_buff offset 1984 in the 2048-byte dev_mem allocation) overflows dev_mem by up to 191 bytes before the post-call

if (ret != ADM1266_BLACKBOX_SIZE)
	return -EIO;

can reject the response.

Contain the fix in the caller without changing the helper signature: read each record into a 255-byte local bounce buffer that matches the helpers maximum output, validate the returned length, and only then copy exactly ADM1266_BLACKBOX_SIZE bytes into the dev_mem slot.

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/43cae21424ff8e33894a0f86c6b80b840c049fd7
• https://git.kernel.org/stable/c/6098634cfa711f11a8d65368dc51ec8f7c8241ba
• https://git.kernel.org/stable/c/60c4b9fe1a3dd012014b1f561a6928a0b5db1126
• https://git.kernel.org/stable/c/7896d87cbb05e097efc113243d4e38f9f8cea16c
• https://git.kernel.org/stable/c/83e039f0a43e0708515b0479cb7690fb93faaaa0
• https://git.kernel.org/stable/c/97a9cf2a8217ca1cdaf48cb9ab26e471632c7e7f
• https://git.kernel.org/stable/c/9d5309500b4607b7198e19f0a3fa13eb864cd5fb
• https://git.kernel.org/stable/c/dd47b8c4a0a8ced442da3f008db28fbbd31feaf0