CVE-2025-21744: linux kernel Null Dereference — Fix

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.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	< 6.1.129
linux	linux_kernel	6.2 — 6.6.78
linux	linux_kernel	6.7 — 6.12.14
linux	linux_kernel	6.13 — 6.13.3

References

Advisories & Patches

https://git.kernel.org/stable/c/3877fc67bd3d5566cc12763bce39710ceb74a97d https://git.kernel.org/stable/c/4e51d6d093e763348916e69d06d87e0a5593661b https://git.kernel.org/stable/c/68abd0c4ebf24cd499841a488b97a6873d5efabb https://git.kernel.org/stable/c/a2beefc4fa49ebc22e664dc6b39dbd054f8488f9 https://git.kernel.org/stable/c/fbbfef2a5b858eab55741a58b2ac9a0cc8d53c58

Other References

https://git.kernel.org/stable/c/2326e19190e176fd72bb542b837a9d2b7fcb8693 https://git.kernel.org/stable/c/59ff4fa653ff6db07c61152516ffba79c2a74bda https://git.kernel.org/stable/c/61541d9b5a23df33934fcc620a3a81f246b1b240 https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Frequently Asked Questions

What is CVE-2025-21744? +

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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21744? +

CVE-2025-21744 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-21744? +

CVE-2025-21744 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21744? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-21744