TP‑Link TL‑WR841N firmware version 13 implements the TDDPv2 debug protocol with DES‑CBC encryption. The cryptographic key used for this protocol is derived from the device's default web management credentials, making it predictable when the router remains in its stock configuration. An attacker that can reach the router over the local network can use this predictable key to decrypt the debug traffic, read sensitive configuration information, change certain configuration values, and force the device to reboot. The result is a loss of integrity of configuration data and a temporary denial‑of‑service condition. The weakness is a predictable cryptographic key (CWE‑1394).

TP‑Link TL‑WR841N router running firmware version 13. No other versions are listed, so the vulnerability applies only to the v13 release of the device.

The CVSS score of 6.1 indicates moderate risk, the EPSS score of less than 1% suggests a low likelihood of exploitation at present. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires the attacker to be on the same local network as the router and to have connectivity to the debug protocol. Once accessed, the attacker can read and modify debug data, alter configuration settings, and trigger a reboot. Because the weakness stems from a predictable key, any user who has not changed the default credentials is at risk.