# CVE-2025-40321: wifi: brcmfmac: fix crash while sending Action Frames in standalone AP Mode

> A remote attacker can crash the Linux kernel by sending a specific Wi-Fi Action frame to a device using the brcmfmac driver in standalone AP mode.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40321, DEBIAN-CVE-2025-40321, GHSA-px3f-ppm2-rx2r, ROOT-OS-DEBIAN-12-CVE-2025-40321, ROOT-OS-DEBIAN-13-CVE-2025-40321, ROOT-OS-UBUNTU-2204-CVE-2025-40321, ROOT-OS-UBUNTU-2404-CVE-2025-40321, UBUNTU-CVE-2025-40321

## What is CVE-2025-40321?

CVE-2025-40321 is a vulnerability in Linux, published on 8 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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]

## Which versions are affected by CVE-2025-40321?


## How do I fix CVE-2025-40321?

Apply the vendor's patch.

## Is CVE-2025-40321 being exploited?

There is no known exploitation of CVE-2025-40321 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40321 and fix it if it is affected.

What it is: CVE-2025-40321 is a vulnerability in Linux, published on 8 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40321 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-40321/ (Markdown: https://insights.sbomify.com/CVE-2025-40321/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40321
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40321
- OSV: https://osv.dev/vulnerability/CVE-2025-40321

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40321/
Summaries are generated and may contain mistakes; the official description above is the record.