# CVE-2026-97953: net: stmmac: fix TX descriptor availability check for TSO traffic

> A flaw in the Linux kernel stmmac driver allows memory corruption via TX ring overwrite when handling highly fragmented TSO traffic, potentially leading to system crashes or code execution.

- **Severity:** High 7.0 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104517, BELL-CVE-2026-97953, DEBIAN-CVE-2026-97953, GHSA-4j3p-7h59-gp38, UBUNTU-CVE-2026-97953

## What is CVE-2026-97953?

CVE-2026-97953 is a high-severity memory corruption vulnerability in Linux, published on 25 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

net: stmmac: fix TX descriptor availability check for TSO traffic

stmmac_tso_xmit() estimates the number of free TX descriptors required by
a TSO skb as:

	(skb->len - proto_hdr_len) / TSO_MAX_BUFF_SIZE + 1

which assumes the payload is split into TSO_MAX_BUFF_SIZE chunks. This
underestimates the descriptors actually consumed by stmmac_tso_allocator(),
since each fragment is mapped individually and so it needs at least one
descriptor regardless of its size. Moreover, one descriptor is used for
the L2/L3/L4 headers and, when the MSS changes, one more is consumed for
the MSS context descriptor.
For a highly fragmented TSO skb the check can therefore pass even when the
ring has too few free slots. stmmac_tso_allocator() then writes past the
available descriptors, overwriting descriptors still owned by the DMA
engine, corrupting the TX ring.
Add stmmac_tso_get_num_desc() to compute the exact number of descriptors
needed for the header, the linear payload and each fragment, plus the MSS
context descriptor when required, and use it in the availability check.

## Which versions are affected by CVE-2026-97953?


## How do I fix CVE-2026-97953?

Apply the vendor's patch.

## Is CVE-2026-97953 being exploited?

There is no known exploitation of CVE-2026-97953 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97953 and fix it if it is affected.

What it is: CVE-2026-97953 is a high-severity memory corruption vulnerability in Linux, published on 25 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97953 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-2026-97953/ (Markdown: https://insights.sbomify.com/CVE-2026-97953/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97953
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97953
- OSV: https://osv.dev/vulnerability/CVE-2026-97953

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97953/
Summaries are generated and may contain mistakes; the official description above is the record.