# CVE-2026-3841: Command Injection Vulnerability in Telnet CLI on TP-Link TL-MR6400

> An authenticated attacker with elevated privileges can execute arbitrary system commands via the Telnet CLI, leading to full device compromise.

- **Severity:** High 8.5 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Mar 2026
- **Updated:** 13 Mar 2026
- **Also known as:** GHSA-ppr5-j2r8-wqw5

## What is CVE-2026-3841?

CVE-2026-3841 is a high-severity command injection vulnerability in TP-Link Systems Inc. TL-MR6400 v5.3, published on 12 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A command injection vulnerability has been identified in the Telnet command-line interface (CLI) of TP-Link TL-MR6400 v5.3.  This issue is caused by insufficient sanitization of data processed during specific CLI operations.  An authenticated attacker with elevated privileges may be able to execute arbitrary system commands.  Successful exploitation may lead to full device compromise, including potential loss of confidentiality, integrity, and availability.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-3841?

It affects 1 product.


Products: Tp-Link Tl-Mr6400 Firmware.

## How do I fix CVE-2026-3841?

No fix has been published for CVE-2026-3841 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3841 being exploited?

There is no known exploitation of CVE-2026-3841 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3841 and fix it if it is affected.

What it is: CVE-2026-3841 is a high-severity command injection vulnerability in TP-Link Systems Inc. TL-MR6400 v5.3, published on 12 Mar 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-2026-3841 in the wild and no public exploit code.

Affected product: TP-Link Systems Inc. TL-MR6400 v5.3. 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-2026-3841/ (Markdown: https://insights.sbomify.com/CVE-2026-3841/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3841
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3841
- OSV: https://osv.dev/vulnerability/CVE-2026-3841

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3841/
Summaries are generated and may contain mistakes; the official description above is the record.