CVE-2026-23396

About vulnerability

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

wifi: mac80211: fix NULL deref in mesh_matches_local()

mesh_matches_local() unconditionally dereferences ie->mesh_config to compare mesh configuration parameters. When called from mesh_rx_csa_frame(), the parsed action-frame elements may not contain a Mesh Configuration IE, leaving ie->mesh_config NULL and triggering a kernel NULL pointer dereference.

The other two callers are already safe:

• ieee80211_mesh_rx_bcn_presp() checks !elems->mesh_config before calling mesh_matches_local()
• mesh_plink_get_event() is only reached through mesh_process_plink_frame(), which checks !elems->mesh_config, too

mesh_rx_csa_frame() is the only caller that passes raw parsed elements to mesh_matches_local() without guarding mesh_config. An adjacent attacker can exploit this by sending a crafted CSA action frame that includes a valid Mesh ID IE but omits the Mesh Configuration IE, crashing the kernel.

The captured crash log:

Oops: general protection fault, probably for non-canonical address … KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] Workqueue: events_unbound cfg80211_wiphy_work […] Call Trace: ? __pfx_mesh_matches_local (net/mac80211/mesh.c:65) ieee80211_mesh_rx_queued_mgmt (net/mac80211/mesh.c:1686) […] ieee80211_iface_work (net/mac80211/iface.c:1754 net/mac80211/iface.c:1802) […] cfg80211_wiphy_work (net/wireless/core.c:426) process_one_work (net/kernel/workqueue.c:3280) ? assign_work (net/kernel/workqueue.c:1219) worker_thread (net/kernel/workqueue.c:3352) ? __pfx_worker_thread (net/kernel/workqueue.c:3385) kthread (net/kernel/kthread.c:436) […] ret_from_fork_asm (net/arch/x86/entry/entry_64.S:255)

This patch adds a NULL check for ie->mesh_config at the top of mesh_matches_local() to return false early when the Mesh Configuration IE is absent.

Affected product:

AlmaLinux 9.2 ESU , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS

Affected packages:

kernel @ 4.18.0 (+15 more)

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

wifi: mac80211: fix NULL deref in mesh_matches_local()

mesh_matches_local() unconditionally dereferences ie->mesh_config to compare mesh configuration parameters. When called from mesh_rx_csa_frame(), the parsed action-frame elements may not contain a Mesh Configuration IE, leaving ie->mesh_config NULL and triggering a kernel NULL pointer dereference.

The other two callers are already safe:

• ieee80211_mesh_rx_bcn_presp() checks !elems->mesh_config before calling mesh_matches_local()
• mesh_plink_get_event() is only reached through mesh_process_plink_frame(), which checks !elems->mesh_config, too

mesh_rx_csa_frame() is the only caller that passes raw parsed elements to mesh_matches_local() without guarding mesh_config. An adjacent attacker can exploit this by sending a crafted CSA action frame that includes a valid Mesh ID IE but omits the Mesh Configuration IE, crashing the kernel.

The captured crash log:

Oops: general protection fault, probably for non-canonical address … KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] Workqueue: events_unbound cfg80211_wiphy_work […] Call Trace: ? __pfx_mesh_matches_local (net/mac80211/mesh.c:65) ieee80211_mesh_rx_queued_mgmt (net/mac80211/mesh.c:1686) […] ieee80211_iface_work (net/mac80211/iface.c:1754 net/mac80211/iface.c:1802) […] cfg80211_wiphy_work (net/wireless/core.c:426) process_one_work (net/kernel/workqueue.c:3280) ? assign_work (net/kernel/workqueue.c:1219) worker_thread (net/kernel/workqueue.c:3352) ? __pfx_worker_thread (net/kernel/workqueue.c:3385) kthread (net/kernel/kthread.c:436) […] ret_from_fork_asm (net/arch/x86/entry/entry_64.S:255)

This patch adds a NULL check for ie->mesh_config at the top of mesh_matches_local() to return false early when the Mesh Configuration IE is absent.