{"id":"CVE-2026-74489","title":"wifi: mac80211: fix tid_tx use-after-free on BA session stop","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: mac80211: fix tid_tx use-after-free on BA session stop\n\nieee80211_stop_tx_ba_cb() hands tid_tx to kfree_rcu() through\nieee80211_remove_tid_tx(), and then reads ti…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 09fc36eec7841cdf732f4db39855e0c73bd075cc","Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 2f067f5a450ea07efd249142a11d940a068fe29c","Linux 7.1"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:58:01.786843Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T19:05:49.622Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74489","references":[{"url":"https://git.kernel.org/stable/c/09fc36eec7841cdf732f4db39855e0c73bd075cc"},{"url":"https://git.kernel.org/stable/c/2f067f5a450ea07efd249142a11d940a068fe29c"}],"tags":["cve.org"],"epss":0.0034,"epssPercentile":0.25965,"ingestedAt":"2026-10-16T19:46:24.359Z","slug":"CVE-2026-74489","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nwifi: mac80211: fix tid_tx use-after-free on BA session stop\n\nieee80211_stop_tx_ba_cb() hands tid_tx to kfree_rcu() through\nieee80211_remove_tid_tx(), and then reads tid_tx->ndp after dropping\nsta->lock:\n\n\tieee80211_remove_tid_tx(sta, tid);\t/* kfree_rcu(tid_tx, rcu_head) */\n\t...\n\tspin_unlock_bh(&sta->lock);\n\n\tif (start_txq)\n\t\tieee80211_agg_start_txq(sta, tid, false);\n\n\tif (send_delba)\n\t\tieee80211_send_delba(..., tid_tx->ndp);\n\nThat read is not covered by an RCU read-side critical section, and it runs\nin preemptible process context: both callers hold the wiphy mutex, reaching\nit either from the ieee80211_ba_session_work() wiphy work or from\nieee80211_sta_tear_down_BA_sessions() during station teardown.\nSoftirqs can run in that window too, both from the local_bh_enable() that\nends ieee80211_agg_start_txq() and from any interrupt exit, so the RCU\ncallback can free tid_tx before the read.\n\nDriving the function from a test module with the grace period forced into\nthat window, KASAN reports the read, and the free arrives on the ordinary\nRCU softirq path:\n\n  BUG: KASAN: slab-use-after-free in ieee80211_stop_tx_ba_cb+0x3cd/0x400\n  Read of size 1 at addr ffff888002b9f52e by task kworker/0:1/10\n  [...]\n  Freed by task 57:\n   __kasan_slab_free+0x47/0x70\n   __rcu_free_sheaf_prepare+0x70/0x250\n   rcu_free_sheaf_nobarn+0x18/0x40\n   rcu_core+0x426/0x1310\n   handle_softirqs+0x144/0x590\n   __irq_exit_rcu+0xea/0x150\n   irq_exit_rcu+0x9/0x20\n   sysvec_apic_timer_interrupt+0x6b/0x80\n   asm_sysvec_apic_timer_interrupt+0x1a/0x20\n\nsend_delba is only set when tx_stop is set, which happens for\nAGG_STOP_LOCAL_REQUEST alone, so this is reached on local teardown -\nsession idle timeout, PTK rekey, suspend, HW reconfig - and not from a\npeer's DELBA.\n\nRead ndp into a local before the session is freed, while sta->lock is still\nheld. tid_tx->ndp has a single writer, in\nieee80211_tx_ba_session_handle_start(), which cannot run concurrently here:\nboth paths are serialised by the wiphy mutex, and the session is already\nmarked HT_AGG_STATE_STOPPING at this point. tid_tx->ndp is also the only\ntid_tx dereference left after ieee80211_remove_tid_tx() in this function.\n\n[move/change the comment a bit to be more general not just on ndp,\n initialize ndp directly]\n\n## Affected\n\n- `Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 09fc36eec7841cdf732f4db39855e0c73bd075cc`\n- `Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 2f067f5a450ea07efd249142a11d940a068fe29c`\n- `Linux 7.1`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}