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Tl Wr841n FirmwareOperating system · Tp Link

CVE-2026-5039

HIGH · 8.8 CVSS v3.1 Published 2026-04-23
Fix available
A fix is available. Upgrade to 231120 or later.
See remediation →
93/100
Remediation priority · Urgent
No privileges 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
TP-Link TL-WR841N v13 uses DES-CBC encryption in the TDDPv2 debug protocol with a cryptographic key derived from default web management credentials, making the key predictable if device is left in default configuration. A network-adjacent attacker can exploit this weakness to gain unauthorized access to the protocol, read debug data, modify certain device configuration values, and trigger device reboot, resulting in loss of integrity and a denial-of-service condition.

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

The TP-Link TL-WR841N v13 router's TDDPv2 debug protocol uses DES-CBC encryption with a cryptographic key derived from the default web management credentials. When these credentials remain unchanged, the encryption key becomes predictable, allowing a network-adjacent attacker to intercept debug data, modify certain configuration parameters, and trigger unauthorized device reboots.

MitigationChange the default web management credentials immediately to render the derived encryption key unpredictable. If no firmware update is available from TP-Link, consider replacing the device as the TDDPv2 protocol design flaw cannot be mitigated through configuration alone.

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 Wr841n FirmwareOperating system
Affected:< 231120

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/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 device model
    Access the router's web management interface or check the device label to confirm the model is TP-Link TL-WR841N v13
    Affected if Device is TL-WR841N v13
  2. Check firmware version
    Log into the router web interface and navigate to Status or System Tools > Firmware Upgrade to view the installed firmware version. Compare against version 231120
    Affected if Firmware version is less than 231120
  3. Verify default credentials in use
    Check the router's admin password setting. If the web management password remains at the factory default (usually admin), the derived DES-CBC encryption key is predictable
    Affected if Web management password is still set to default
  4. Confirm TDDPv2 service exposure
    Check if the TDDPv2 debug service (typically listens on UDP port 25439) is accessible from the network. This may require checking router firewall settings or scanning the device UDP port 25439
    Affected if TDDPv2 service is reachable from an attacker-adjacent network position

You are affected if you have a TL-WR841N v13 router running firmware below version 231120 AND the web management password is still at its default setting, with TDDPv2 accessible on the network.

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 231120 or later
Fixed in 231120
Interim mitigation

Change the default web management credentials immediately to render the derived encryption key unpredictable. If no firmware update is available from TP-Link, consider replacing the device as the TDDPv2 protocol design flaw cannot be mitigated through configuration alone.

Recommended fix Moderate confidence

TL-WR841N v13 firmware version 231120 or later

  1. 1. Access the TP-Link TL-WR841N v13 router web management interface
  2. 2. Navigate to the firmware upgrade section (typically under System Tools > Firmware Upgrade)
  3. 3. Download the latest firmware version from the official TP-Link support website for the TL-WR841N v13
  4. 4. Upload and apply the firmware update, ensuring power is not interrupted during the process
  5. 5. After reboot, verify the firmware version has been updated to 231120 or later
  6. 6. After upgrading, change the default admin credentials to a strong, unique password to further harden the device
Caveat Ensure stable power during firmware upgrade to avoid bricking the device; some legacy features may be deprecated in newer firmware

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

Fix this in Tl Wr841n Firmware Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,696.

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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-2026-5039 in production — separate from our analysis above.

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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