Medium [CVE-2026-64223] consume only present negotiated TTLM maps

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: consume only present negotiated TTLM maps ieee80211_tid_to_link_map_size_ok() validates negotiated TTLM elements against the number of link-map entries indicated by link_map_presence. ieee80211_parse_neg_ttlm() must consume the same layout.

The parser advanced its cursor for every TID, including TIDs whose presence bit is clear and therefore have no map bytes in the element. A sparse map can then make a later present TID read past the validated element.

The bad bytes land in neg_ttlm->{up,down}link[tid] but are gated by valid_links before being applied to driver state, so a peer cannot turn the read into a policy change.

Under KUnit + KASAN with an exact-sized element allocation the OOB read is reported as a slab-out-of-bounds; whether the same trigger fires under the production RX path depends on surrounding allocator state. Advance the cursor only when the current TID has a map present.

This vulnerability, an out-of-bounds read, occurs when parsing negotiated Time-To-Live Map (TTLM) elements. A remote attacker could craft a sparse map, causing the parser to read beyond the intended memory boundary.

While direct policy changes are prevented, this issue can lead to memory corruption, potentially impacting system stability.