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Tl Mr6400 FirmwareOperating system · Tp Link

CVE-2026-3841

HIGH · 8.8 CVSS v3.1 Published 2026-03-12
Fix available
A fix is available. Upgrade to 1.9.0 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Command injection vulnerability in the Telnet CLI of TP-Link TL-MR6400 v5.3 caused by insufficient input sanitization during CLI operations, allowing authenticated attackers with elevated privileges to execute arbitrary system commands.

MitigationApply vendor-supplied firmware patch when available; otherwise disable Telnet access and enforce strict network access controls to limit exposure to trusted users only.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Tl Mr6400 FirmwareOperating system
Affected:< 1.9.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed firmware version
    Access the router admin web interface (usually at 192.168.0.1) and navigate to Status or System settings to view the firmware version. Alternatively, log into the device via console/Telnet and run 'version' or 'cat /proc/version' if accessible.
    Affected if The firmware version is lower than 1.9.0 (e.g., v1.0, v1.1, v1.2, v5.0, v5.1, v5.2, v5.3).
  2. Confirm Telnet service is enabled
    Check the router admin interface under Advanced or System Tools for Telnet/SSH service settings. If Telnet is listed as enabled or active, the device exposes the vulnerable service.
    Affected if Telnet service is enabled on the device (regardless of whether remote access is permitted).
  3. Verify Telnet access restrictions
    In the router admin interface, check if Telnet is restricted to LAN-side access only or if it allows WAN/remote management. Look for settings named 'Remote Management', 'Telnet Access', or similar.
    Affected if Telnet is accessible from WAN interfaces or from any IP address rather than being restricted to trusted LAN IPs only.
  4. Check administrative account privileges
    Review the list of administrative accounts in the router settings. Identify whether any account has 'Super Admin' or elevated privileges enabled, as the CVE requires an authenticated attacker with elevated privileges.
    Affected if There exists an administrative account with elevated privileges (Super Admin, root-level, or full administrative access) configured on the device.

The device is affected if the installed firmware version is below 1.9.0 AND Telnet service is enabled, especially if accessible from untrusted networks or with elevated privilege accounts present.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.9.0 or later
Fixed in 1.9.0
Interim mitigation

Apply vendor-supplied firmware patch when available; otherwise disable Telnet access and enforce strict network access controls to limit exposure to trusted users only.

Recommended fix Moderate confidence

TL-MR6400 Firmware 1.9.0

  1. Access the TP-Link TL-MR6400 router web management interface through a browser
  2. Navigate to the System or Administration section, then locate the Firmware Upgrade option
  3. Download the official TL-MR6400 firmware version 1.9.0 or later from the TP-Link support website (support.tp-link.com)
  4. In the web interface, select the downloaded firmware file and initiate the upgrade process
  5. Wait for the upgrade to complete - do not power off the device during this process
  6. After reboot, verify the firmware version in the router interface to confirm the update was successful
  7. Consider changing administrator credentials post-upgrade as a security best practice
Caveat Firmware upgrades may reset some configurations to defaults; back up current settings before upgrading if possible

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Tl Mr6400 Firmware Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,280
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-3841 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data