# CVE-2026-72157: net: thunderbolt: Fix frags[] overflow by bounding frame_count

> A remote attacker can trigger a buffer overflow in the Thunderbolt network driver by sending crafted multi-frame packets, potentially leading to memory corruption and code execution.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72157, DEBIAN-CVE-2026-72157, GHSA-8f5r-c72f-67g5, UBUNTU-CVE-2026-72157

## What is CVE-2026-72157?

CVE-2026-72157 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. 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:

net: thunderbolt: Fix frags[] overflow by bounding frame_count

tbnet_poll() assembles a multi-frame ThunderboltIP packet into one skb. The
first frame goes into the skb linear area and every further frame is added as
a page fragment.

	skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
			page, hdr_size, frame_size,
			TBNET_RX_PAGE_SIZE - hdr_size);

A packet of frame_count frames therefore ends up with frame_count - 1
fragments. tbnet_check_frame() only bounds the peer supplied frame_count to
TBNET_RING_SIZE / 4 (64), which is far above MAX_SKB_FRAGS (17 by default). A
peer that sends a packet of 19 or more small frames pushes nr_frags past
MAX_SKB_FRAGS, so skb_add_rx_frag() writes past skb_shinfo()->frags[] and
corrupts memory after the shared info.

Tighten the start of packet bound to MAX_SKB_FRAGS + 1 so a packet can never
produce more fragments than frags[] can hold. This matches the recent skb
frags overflow fixes in other receive paths, for example f0813bcd2d9d ("net:
wwan: t7xx: fix potential skb->frags overflow in RX path") and 600dc40554dc
("net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()").

## Which versions are affected by CVE-2026-72157?


## How do I fix CVE-2026-72157?

Apply the vendor's patch.

## Is CVE-2026-72157 being exploited?

There is no known exploitation of CVE-2026-72157 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72157 and fix it if it is affected.

What it is: CVE-2026-72157 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72157 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72157/ (Markdown: https://insights.sbomify.com/CVE-2026-72157/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72157
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72157
- OSV: https://osv.dev/vulnerability/CVE-2026-72157

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72157/
Summaries are generated and may contain mistakes; the official description above is the record.