CVE-2026-23279

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

wifi: mac80211: fix NULL pointer dereference in mesh_rx_csa_frame()

In mesh_rx_csa_frame(), elems->mesh_chansw_params_ie is dereferenced

at lines 1638 and 1642 without a prior NULL check:

ifmsh->chsw_ttl = elems->mesh_chansw_params_ie->mesh_ttl;

...

pre_value = le16_to_cpu(elems->mesh_chansw_params_ie->mesh_pre_value);

The mesh_matches_local() check above only validates the Mesh ID,

Mesh Configuration, and Supported Rates IEs. It does not verify the

presence of the Mesh Channel Switch Parameters IE (element ID 118).

When a received CSA action frame omits that IE, ieee802_11_parse_elems()

leaves elems->mesh_chansw_params_ie as NULL, and the unconditional

dereference causes a kernel NULL pointer dereference.

A remote mesh peer with an established peer link (PLINK_ESTAB) can

trigger this by sending a crafted SPECTRUM_MGMT/CHL_SWITCH action frame

that includes a matching Mesh ID and Mesh Configuration IE but omits the

Mesh Channel Switch Parameters IE. No authentication beyond the default

open mesh peering is required.

Crash confirmed on kernel 6.17.0-5-generic via mac80211_hwsim:

BUG: kernel NULL pointer dereference, address: 0000000000000000

Oops: Oops: 0000 [#1] SMP NOPTI

RIP: 0010:ieee80211_mesh_rx_queued_mgmt+0x143/0x2a0 [mac80211]

CR2: 0000000000000000

Fix by adding a NULL check for mesh_chansw_params_ie after

mesh_matches_local() returns, consistent with how other optional IEs

are guarded throughout the mesh code.

The bug has been present since v3.13 (released 2014-01-19).