CVE-2026-63996

Status: UPDATED  |  Advisory ID: CVE-2026-63996

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

ethtool: cmis: require exact CDB reply length

Malicious SFP module could respond with rpl_len longer than

what cmis_cdb_process_reply() expected, leading to OOB writes.

Malicious HW is a bit theoretical but some modules may just

be buggy and/or the reads may occasionally get corrupted,

so let's protect the kernel.

The existing check protects from short replies. We need to

protect from long ones, too. All callers that pass a non-zero

rpl_exp_len cast the reply payload to a fixed-layout struct

and read fields at fixed offsets, with no version negotiation

or short-reply handling:

- cmis_cdb_validate_password()

- cmis_cdb_module_features_get()

- cmis_fw_update_fw_mng_features_get()

so let's assume that responses longer than expected do not

have to be handled gracefully here. Add a warning message

to make the debug easier in case my understanding is wrong...

Note that page_data->length (argument of kmalloc) comes from

last arg to ethtool_cmis_page_init() which is rpl_exp_len.

Note2 that AIs also like to point out overflows in args->req.payload

itself (which is a fixed-size 120 B buffer, on the stack),

but callers should be reading structs defined by the standard,

so protecting from requests for more data than max seem like

defensive programming. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References