# CVE-2026-109588: Numeric truncation in the MPU buffer authorization check in FreeRTOS-Kernel

> An integer truncation flaw in FreeRTOS allows unprivileged tasks to access privileged kernel memory via stream buffer calls on specific Arm Cortex-R82 MPU builds.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA: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:** No
- **Published:** 16 Oct 2026
- **Updated:** 20 Oct 2026
- **Also known as:** GHSA-qf4j-6f5j-876g

## What is CVE-2026-109588?

CVE-2026-109588 is a critical vulnerability in FreeRTOS-Kernel, published on 16 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Numeric truncation of the buffer length in the MPU buffer authorization check in FreeRTOS-Kernel V11.3.0 and V11.3.1 on the Arm Cortex-R82 (Armv8-R AArch64) MPU port might allow, under certain conditions, an unprivileged task on MPU-enabled builds to read or write privileged kernel memory beyond the validated buffer window, via a stream buffer system call.

To remediate this issue, users should upgrade to version V11.3.2 or later.

Weakness: CWE-787 (Out-of-bounds Write), CWE-197 (Numeric Truncation Error), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-109588?


## How do I fix CVE-2026-109588?

No fix has been published for CVE-2026-109588 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-109588 being exploited?

There is no known exploitation of CVE-2026-109588 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109588 and fix it if it is affected.

What it is: CVE-2026-109588 is a critical vulnerability in FreeRTOS-Kernel, published on 16 Oct 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-2026-109588 in the wild and no public exploit code.

Affected product: FreeRTOS-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-2026-109588/ (Markdown: https://insights.sbomify.com/CVE-2026-109588/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109588
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109588
- OSV: https://osv.dev/vulnerability/CVE-2026-109588

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109588/
Summaries are generated and may contain mistakes; the official description above is the record.