# CVE-2026-42021: Multiple stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup static network configuration functionality of Totolink X


- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 20 Oct 2026
- **Updated:** 23 Oct 2026
- **Also known as:** GHSA-9hw7-42mj-hjfc

## What is CVE-2026-42021?

CVE-2026-42021 is a critical vulnerability in Totolink, published on 20 Oct 2026. 

### Official description

Multiple stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup static network configuration functionality of Totolink X2000R TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. A specially crafted HTTP request can lead to arbitrary code execution. An attacker can make an authenticated HTTP request to trigger these vulnerabilities. This vulnerability concerns the static_dns1 parameter.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-42021?


## How do I fix CVE-2026-42021?

No fix has been published for CVE-2026-42021 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42021 being exploited?

There is no known exploitation of CVE-2026-42021 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42021 and fix it if it is affected.

What it is: CVE-2026-42021 is a critical vulnerability in Totolink, published on 20 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-42021 in the wild and no public exploit code.

Affected product: Totolink. 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-2026-42021/ (Markdown: https://insights.sbomify.com/CVE-2026-42021/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42021
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42021
- OSV: https://osv.dev/vulnerability/CVE-2026-42021

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42021/
Summaries are generated and may contain mistakes; the official description above is the record.