High [CVE-2026-68409] Use-after-free vulnerability in mac80211 Wi-Fi driver

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: defer link RX stats percpu free to RCU sta_remove_link() frees a removed MLO link's RX stats percpu buffer right away, but defers only the link container to RCU: sta_info_free_link(&alloc->info); kfree_rcu(alloc, rcu_head); The RX fast path reads link_sta under rcu_read_lock and writes the percpu stats.

A reader that resolved link_sta before the removal keeps the pointer. The container stays alive from the kfree_rcu, so the read still works.

But the percpu block it points to is already freed. This needs uses_rss.

That is when pcpu_rx_stats exists. The full STA teardown frees the deflink stats only after synchronize_net().

The link removal path had no such barrier. The race is hard to win in practice, but the free should still wait for RCU.

Free the link together with its data from a single RCU callback, so the percpu block is reclaimed only after readers drain. When an MLO (Multi-Link Operation) link is removed, the RX statistics per-CPU buffer is freed immediately, while the link container is deferred to RCU (Read-Copy-Update).

This timing issue can lead to a use-after-free vulnerability, where a reader might still access the freed memory. While difficult to exploit in practice, this could potentially lead to system instability or denial of service.