# CVE-2026-43491: net: qrtr: ns: Limit the maximum server registration per node

> A malicious client can exhaust kernel memory by flooding server registration messages in the QRTR network subsystem, causing a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 May 2026
- **Updated:** 19 Aug 2026
- **Also known as:** AZL-86981, BELL-CVE-2026-43491, DEBIAN-CVE-2026-43491, GHSA-vfqf-4c37-r857, ROOT-OS-DEBIAN-11-CVE-2026-43491, ROOT-OS-DEBIAN-12-CVE-2026-43491, ROOT-OS-UBUNTU-2204-CVE-2026-43491, ROOT-OS-UBUNTU-2404-CVE-2026-43491, UBUNTU-CVE-2026-43491

## What is CVE-2026-43491?

CVE-2026-43491 is a medium-severity denial of service vulnerability in Linux kernel, published on 19 May 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: qrtr: ns: Limit the maximum server registration per node

Current code does no bound checking on the number of servers added per
node. A malicious client can flood NEW_SERVER messages and exhaust memory.

Fix this issue by limiting the maximum number of server registrations to
256 per node. If the NEW_SERVER message is received for an old port, then
don't restrict it as it will get replaced. While at it, also rate limit
the error messages in the failure path of qrtr_ns_worker().

Note that the limit of 256 is chosen based on the current platform
requirements. If requirement changes in the future, this limit can be
increased.

## Which versions are affected by CVE-2026-43491?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43491?

Apply the vendor's patch.

## Is CVE-2026-43491 being exploited?

There is no known exploitation of CVE-2026-43491 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43491 and fix it if it is affected.

What it is: CVE-2026-43491 is a medium-severity denial of service vulnerability in Linux kernel, published on 19 May 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-2026-43491 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43491/ (Markdown: https://insights.sbomify.com/CVE-2026-43491/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43491
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43491
- OSV: https://osv.dev/vulnerability/CVE-2026-43491

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43491/
Summaries are generated and may contain mistakes; the official description above is the record.