Advisory [CVE-2026-64440] fix OOB write in HT_caps_handler

In the Linux kernel, the following vulnerability has been resolved: staging: rtl8723bs: fix OOB write in HT_caps_handler() HT_caps_handler() iterates pIE->length bytes and writes into HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct HT_caps_element).

Because pIE->length is a raw u8 from an over-the-air 802.11 AssocResponse frame and is never validated, a malicious AP can set it up to 255, causing up to 229 bytes of out-of-bounds writes into adjacent fields of struct mlme_ext_info.

Truncate the iteration count to the size of HT_caps.u.HT_cap using umin() so that data from a longer-than-expected IE is silently ignored rather than written out of bounds, preserving interoperability with APs that pad the element.

An early return on oversized IEs was considered but rejected: it would bypass the pmlmeinfo->HT_caps_enable = 1 assignment that precedes the loop, silently disabling HT mode for APs that append extra bytes to the HT Capabilities IE. A remote attacker, by operating a malicious Access Point (AP), can send a specially crafted 802.11 AssocResponse frame.

This can trigger an out-of-bounds write vulnerability in the `HT_caps_handler()` function, leading to memory corruption. This memory corruption could allow an attacker to cause a denial of service or potentially execute arbitrary code.

Red Hat severity: not rated. Weakness: CWE-787.