# CVE-2026-7426: Out-of-Bounds Write via Unsanitized Prefix Length in Router Advertisement Processing in FreeRTOS-Plus-TCP

> An adjacent attacker can cause heap buffer overflow and potential code execution by sending crafted IPv6 Router Advertisements to devices using FreeRTOS-Plus-TCP.

- **Severity:** Medium 6.1 (`CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Apr 2026
- **Updated:** 29 Apr 2026
- **Also known as:** GHSA-97qg-4359-xm3x

## What is CVE-2026-7426?

CVE-2026-7426 is a medium-severity memory corruption vulnerability in AWS FreeRTOS-Plus-TCP, published on 29 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Insufficient validation of the prefix length field in IPv6 Router Advertisement processing in FreeRTOS-Plus-TCP before V4.2.6 and V4.4.1 allows an adjacent network actor to cause memory corruption by sending a crafted Router Advertisement with a prefix length value exceeding the maximum valid length, resulting in a heap buffer overflow. Users processing IPv4 RA only are not impacted.

To mitigate this issue, users should upgrade to the fixed version when available.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-7426?

It affects 1 product.


Products: Amazon Freertos-Plus-Tcp.

## How do I fix CVE-2026-7426?

No fix has been published for CVE-2026-7426 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-7426 being exploited?

There is no known exploitation of CVE-2026-7426 in the wild and no public exploit code.

## Other vulnerabilities in AWS FreeRTOS-Plus-TCP

- [CVE-2024-38373](https://insights.sbomify.com/CVE-2024-38373/): FreeRTOS-Plus-TCP Buffer Over-Read in DNS Response Parser (critical 9.6)
- [CVE-2026-7424](https://insights.sbomify.com/CVE-2026-7424/): Integer Underflow in DHCPv6 Sub-Option Parser in FreeRTOS-Plus-TCP (high 7.2)
- [CVE-2026-7422](https://insights.sbomify.com/CVE-2026-7422/): MAC Address Validation Bypass in FreeRTOS-Plus-TCP IPv4 and IPv6 Packet Processing (high 7.1)
- [CVE-2026-7423](https://insights.sbomify.com/CVE-2026-7423/): Integer Underflow in ICMP Echo Reply Processing in FreeRTOS-Plus-TCP (medium 6.0)
- [CVE-2026-7425](https://insights.sbomify.com/CVE-2026-7425/): Out-of-Bounds Read in Router Advertisement Option Parser in FreeRTOS-Plus-TCP (medium 6.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-7426 and fix it if it is affected.

What it is: CVE-2026-7426 is a medium-severity memory corruption vulnerability in AWS FreeRTOS-Plus-TCP, published on 29 Apr 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-2026-7426 in the wild and no public exploit code.

Affected product: AWS FreeRTOS-Plus-TCP. 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-2026-7426/ (Markdown: https://insights.sbomify.com/CVE-2026-7426/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-7426
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-7426
- OSV: https://osv.dev/vulnerability/CVE-2026-7426

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-7426/
Summaries are generated and may contain mistakes; the official description above is the record.