# CVE-2026-4566: Belkin F9K1122 formWISP5G stack-based overflow

> Remote attackers can trigger a stack-based buffer overflow in the Belkin F9K1122 router's WISP configuration interface, potentially leading to arbitrary code execution.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Mar 2026
- **Updated:** 23 Mar 2026
- **Also known as:** GHSA-9c76-c4x3-j7c2

## What is CVE-2026-4566?

CVE-2026-4566 is a high-severity memory corruption vulnerability in Belkin F9K1122, published on 23 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A flaw has been found in Belkin F9K1122 1.00.33. The affected element is the function formWISP5G of the file /goform/formWISP5G. Executing a manipulation of the argument webpage can lead to stack-based buffer overflow. The attack can be launched remotely. The exploit has been published and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-121 (Stack-based Buffer Overflow), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-4566?

It affects 1 product.


Products: Belkin F9k1122 Firmware.

## How do I fix CVE-2026-4566?

No fix has been published for CVE-2026-4566 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4566 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4566 exists.

## Other vulnerabilities in Belkin F9K1122

- [CVE-2026-5608](https://insights.sbomify.com/CVE-2026-5608/): Belkin F9K1122 formWlanSetup stack-based overflow (high 8.7)
- [CVE-2026-5042](https://insights.sbomify.com/CVE-2026-5042/): Belkin F9K1122 Parameter formCrossBandSwitch stack-based overflow (high 8.7)
- [CVE-2026-5043](https://insights.sbomify.com/CVE-2026-5043/): Belkin F9K1122 Parameter formSetPassword stack-based overflow (high 8.7)
- [CVE-2026-5044](https://insights.sbomify.com/CVE-2026-5044/): Belkin F9K1122 Setting formSetSystemSettings stack-based overflow (high 8.7)
- [CVE-2025-7084](https://insights.sbomify.com/CVE-2025-7084/): Belkin F9K1122 webs formWpsStart stack-based overflow (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4566 and fix it if it is affected.

What it is: CVE-2026-4566 is a high-severity memory corruption vulnerability in Belkin F9K1122, published on 23 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-4566 exists.

Affected product: Belkin F9K1122. 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-2026-4566/ (Markdown: https://insights.sbomify.com/CVE-2026-4566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4566
- OSV: https://osv.dev/vulnerability/CVE-2026-4566

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4566/
Summaries are generated and may contain mistakes; the official description above is the record.