# CVE-2026-31616

> Vulnerability · severity: **MEDIUM** (CVSS 5.5).

## 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").

## Key facts

- **CVE ID:** CVE-2026-31616
- **Published:** 2026-04-24
- **CVSS severity:** MEDIUM
- **CVSS base score:** 5.5
- **CWE codes:** CWE-401

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31616

## Citation

> AI Analytics. CVE-2026-31616. Retrieved 2026-08-08 from https://api.ai-analytics.org/cve/CVE-2026-31616. Derived from NIST NVD. Licensed CC0.

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