# CVE-2026-89743: misc: nsm: bound the device-reported response length

> A malicious NSM device can trigger an out-of-bounds read in the Linux kernel, disclosing adjacent kernel heap memory to user space.

- **Severity:** High 7.7 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89743, DEBIAN-CVE-2026-89743, GHSA-ggmc-fhxw-v94j, UBUNTU-CVE-2026-89743

## What is CVE-2026-89743?

CVE-2026-89743 is a high-severity vulnerability in Linux, published on 11 Sep 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:

misc: nsm: bound the device-reported response length

nsm_sendrecv_msg_locked() stores the virtqueue used-ring length reported
by the NSM device into msg->resp.len without bounding it to the response
buffer. A malicious or buggy backend can report a length larger than the
response buffer; parse_resp_raw() then copies that many bytes out of the
fixed buffer to user space, disclosing adjacent kernel heap (an
out-of-bounds read). The request path already floors its length in
fill_req_raw(); the response path lacks the symmetric check.

Clamp the stored length to the size of the response buffer. Well-behaved
devices report no more than the posted buffer size, so conforming traffic
is unaffected.

## Which versions are affected by CVE-2026-89743?


## How do I fix CVE-2026-89743?

Apply the vendor's patch.

## Is CVE-2026-89743 being exploited?

There is no known exploitation of CVE-2026-89743 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89743 and fix it if it is affected.

What it is: CVE-2026-89743 is a high-severity vulnerability in Linux, published on 11 Sep 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-2026-89743 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-2026-89743/ (Markdown: https://insights.sbomify.com/CVE-2026-89743/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89743
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89743
- OSV: https://osv.dev/vulnerability/CVE-2026-89743

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89743/
Summaries are generated and may contain mistakes; the official description above is the record.