CVE-2025-21744 wifi: brcmfmac: fix NULL pointer dereference in brcmf_txfinalize()

What is CVE-2025-21744?

CVE-2025-21744 is a medium-severity vulnerability in Linux kernel, published on 27 Feb 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 NULL pointer dereference in brcmf_txfinalize()

On removal of the device or unloading of the kernel module a potential NULL pointer dereference occurs.

The following sequence deletes the interface:

brcmf_detach() brcmf_remove_interface() brcmf_del_if()

Inside the brcmf_del_if() function the drvr->if2bss[ifidx] is updated to BRCMF_BSSIDX_INVALID (-1) if the bsscfgidx matches.

After brcmf_remove_interface() call the brcmf_proto_detach() function is called providing the following sequence:

brcmf_detach() brcmf_proto_detach() brcmf_proto_msgbuf_detach() brcmf_flowring_detach() brcmf_msgbuf_delete_flowring() brcmf_msgbuf_remove_flowring() brcmf_flowring_delete() brcmf_get_ifp() brcmf_txfinalize()

Since brcmf_get_ip() can and actually will return NULL in this case the call to brcmf_txfinalize() will result in a NULL pointer dereference inside brcmf_txfinalize() when trying to update ifp->ndev->stats.tx_errors.

This will only happen if a flowring still has an skb.

Although the NULL pointer dereference has only been seen when trying to update the tx statistic, all other uses of the ifp pointer have been guarded as well with an early return if ifp is NULL.

Weakness: CWE-476

Which versions are affected by CVE-2025-21744?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21744?

Apply the vendor's patch.

Is CVE-2025-21744 being exploited?

There is no known exploitation of CVE-2025-21744 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-57914, BELL-CVE-2025-21744, DEBIAN-CVE-2025-21744, GHSA-xqj4-x748-chwg, ROOT-OS-UBUNTU-2404-CVE-2025-21744, UBUNTU-CVE-2025-21744.