CVE-2026-31616

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_phonet: fix skb frags[] overflow in pn_rx_complete()

A broken/bored/mean USB host can overflow the skb_shared_info->frags[]

array on a Linux gadget exposing a Phonet function by sending an

unbounded sequence of full-page OUT transfers.

pn_rx_complete() finalizes the skb only when req->actual < req->length,

where req->length is set to PAGE_SIZE by the gadget. If the host always

sends exactly PAGE_SIZE bytes per transfer, fp->rx.skb will never be

reset and each completion will add another fragment via

skb_add_rx_frag(). Once nr_frags exceeds MAX_SKB_FRAGS (default 17),

subsequent frag stores overwrite memory adjacent to the shinfo on the

heap.

Drop the skb and account a length error when the frag limit is reached,

matching the fix applied in t7xx by commit f0813bcd2d9d ("net: wwan:

t7xx: fix potential skb->frags overflow in RX path").

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References