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).

Weakness

The product dereferences a pointer that it expects to be valid but is NULL.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/017c1792525064a723971f0216e6ef86a8c7af11
• https://git.kernel.org/stable/c/22a9adea7e26d236406edc0ea00b54351dd56b9c
• https://git.kernel.org/stable/c/2b5f282b1b7241ef624c3399a1cdff0bb1a3eeab
• https://git.kernel.org/stable/c/753ad20dcbe36b67088c7770d8fc357d7cc43e08
• https://git.kernel.org/stable/c/be8b82c567fda86f2cbb43b7208825125bb31421
• https://git.kernel.org/stable/c/cc6d5a3c0a854aeae00915fc5386570c86029c60
• https://git.kernel.org/stable/c/f061336f072ab03fd29270ae61fede46bf8fd69d
• https://git.kernel.org/stable/c/f5d8af683410a8c82e48b51291915bd612523d9a