CVE-2021-43976: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-43976 affects the Linux kernel through version 5.15.2, specifically in the mwifiexusbrecv function within drivers/net/wireless/marvell/mwifiex/usb.c. The vulnerability was discovered by Zekun Shen and Brendan Dolan-Gavitt and was disclosed in November 2021 (Kernel Commit).

The vulnerability occurs when mwifiexusbrecv encounters an unknown recvtype and returns -1 without restoring the skb (socket buffer). When mwifiexusbrxcomplete is subsequently called with the same skb, calling skbput causes an skbover_panic condition. The vulnerability has a CVSS v3.1 base score of 4.6 (MEDIUM) with vector AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (NVD).

A successful exploit of this vulnerability allows an attacker with physical access to cause a denial of service (system crash) by connecting a crafted USB device (Debian Advisory, NetApp Advisory).

The vulnerability was fixed in the Linux kernel by modifying the mwifiexusbrecv function to properly restore the skb before returning on error. The fix was committed to the kernel and has been backported to various distributions including Debian, Ubuntu, and Fedora (Debian Advisory, Fedora Update).