CVE-2025-40321
Description
In the Linux kernel, the following vulnerability has been resolved:
wifi: brcmfmac: fix crash while sending Action Frames in standalone AP Mode
Currently, whenever there is a need to transmit an Action frame, the brcmfmac driver always uses the P2P vif to send the "actframe" IOVAR to firmware. The P2P interfaces were available when wpa_supplicant is managing the wlan interface.
However, the P2P interfaces are not created/initialized when only hostapd is managing the wlan interface. And if hostapd receives an ANQP Query REQ Action frame even from an un-associated STA, the brcmfmac driver tries to use an uninitialized P2P vif pointer for sending the IOVAR to firmware. This NULL pointer dereferencing triggers a driver crash.
[ 1417.074538] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [...] [ 1417.075188] Hardware name: Raspberry Pi 4 Model B Rev 1.5 (DT) [...] [ 1417.075653] Call trace: [ 1417.075662] brcmf_p2p_send_action_frame+0x23c/0xc58 [brcmfmac] [ 1417.075738] brcmf_cfg80211_mgmt_tx+0x304/0x5c0 [brcmfmac] [ 1417.075810] cfg80211_mlme_mgmt_tx+0x1b0/0x428 [cfg80211] [ 1417.076067] nl80211_tx_mgmt+0x238/0x388 [cfg80211] [ 1417.076281] genl_family_rcv_msg_doit+0xe0/0x158 [ 1417.076302] genl_rcv_msg+0x220/0x2a0 [ 1417.076317] netlink_rcv_skb+0x68/0x140 [ 1417.076330] genl_rcv+0x40/0x60 [ 1417.076343] netlink_unicast+0x330/0x3b8 [ 1417.076357] netlink_sendmsg+0x19c/0x3f8 [ 1417.076370] __sock_sendmsg+0x64/0xc0 [ 1417.076391] ____sys_sendmsg+0x268/0x2a0 [ 1417.076408] ___sys_sendmsg+0xb8/0x118 [ 1417.076427] __sys_sendmsg+0x90/0xf8 [ 1417.076445] __arm64_sys_sendmsg+0x2c/0x40 [ 1417.076465] invoke_syscall+0x50/0x120 [ 1417.076486] el0_svc_common.constprop.0+0x48/0xf0 [ 1417.076506] do_el0_svc+0x24/0x38 [ 1417.076525] el0_svc+0x30/0x100 [ 1417.076548] el0t_64_sync_handler+0x100/0x130 [ 1417.076569] el0t_64_sync+0x190/0x198 [ 1417.076589] Code: f9401e80 aa1603e2 f9403be1 5280e483 (f9400000)
Fix this, by always using the vif corresponding to the wdev on which the Action frame Transmission request was initiated by the userspace. This way, even if P2P vif is not available, the IOVAR is sent to firmware on AP vif and the ANQP Query RESP Action frame is transmitted without crashing the driver.
Move init_completion() for "send_af_done" from brcmf_p2p_create_p2pdev() to brcmf_p2p_attach(). Because the former function would not get executed when only hostapd is managing wlan interface, and it is not safe to do reinit_completion() later in brcmf_p2p_tx_action_frame(), without any prior init_completion().
And in the brcmf_p2p_tx_action_frame() function, the condition check for P2P Presence response frame is not needed, since the wpa_supplicant is properly sending the P2P Presense Response frame on the P2P-GO vif instead of the P2P-Device vif.
[Cc stable]
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
In brcmfmac, sending Action Frames in standalone AP mode (hostapd) causes a NULL pointer dereference because the driver incorrectly uses an uninitialized P2P vif.
Vulnerability
In the Linux kernel's brcmfmac Wi-Fi driver, a NULL pointer dereference occurs when the driver attempts to transmit an Action Frame while operating in standalone AP mode managed solely by hostapd. The root cause is that the driver always uses the P2P virtual interface (vif) to send the "actframe" IOVAR to firmware, but P2P interfaces are only created when wpa_supplicant manages the interface. When only hostapd is in use, the P2P vif pointer remains uninitialized, leading to a crash upon dereference [1][2][3][4].
Exploitation
An attacker can trigger this vulnerability by sending an ANQP Query Request Action frame to a device running hostapd on a brcmfmac-based wireless interface. No authentication is required; the frame can be sent from an unassociated station. The attack surface is local network access, as the attacker must be within Wi-Fi range to transmit the malicious frame. The crash occurs in the kernel context, causing a denial of service (system panic or driver hang).
Impact
Successful exploitation results in a kernel NULL pointer dereference, leading to a system crash or hang. This constitutes a denial-of-service (DoS) condition. The crash trace shows the fault in brcmf_p2p_send_action_frame called from brcmf_cfg80211_mgmt_tx. The impact is limited to systems using the brcmfmac driver in standalone AP mode (e.g., Raspberry Pi 4 with hostapd).
Mitigation
The fix has been applied in the Linux kernel stable tree via commits that ensure the driver uses the correct vif (the AP vif) for sending action frames when P2P is not available. Users should update to a kernel version containing the fix. No workaround is documented; the vulnerability is patched in the referenced commits [1][2][3][4].
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
8c863b9c7b4e9e1fc9afcce9155f60a72a178c2b0f8d3e73564e3175d1c8aa6eed58249e7dbc7357b6aae3776c685ebe5Vulnerability mechanics
Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
8- git.kernel.org/stable/c/3776c685ebe5f43e9060af06872661de55e80b9anvd
- git.kernel.org/stable/c/55f60a72a178909ece4e32987e4c642ba57e1cf4nvd
- git.kernel.org/stable/c/64e3175d1c8a3bea02032e7c9d1befd5f43786fanvd
- git.kernel.org/stable/c/a6eed58249e7d60f856900e682992300f770f64bnvd
- git.kernel.org/stable/c/c2b0f8d3e7358c33d90f0e62765d474f25f26a45nvd
- git.kernel.org/stable/c/c863b9c7b4e9af0b7931cb791ec91971a50f1a25nvd
- git.kernel.org/stable/c/dbc7357b6aae686d9404e1dd7e2e6cf92c3a1b5anvd
- git.kernel.org/stable/c/e1fc9afcce9139791260f962541282d47fbb508dnvd
News mentions
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