Overview
CVE-2025-11676 is a critical vulnerability affecting TP-Link TL-WR940N V6 routers, specifically those running firmware versions up to and including Build 220801. This vulnerability allows unauthenticated adjacent attackers to perform a Denial of Service (DoS) attack by exploiting an improper input validation issue within the UPnP modules of the device. This means that an attacker within the same network as the router can render it unresponsive, disrupting internet access for all connected devices.
Technical Details
The vulnerability stems from insufficient input validation within the UPnP (Universal Plug and Play) service implementation on the TP-Link TL-WR940N V6. UPnP is designed to allow devices to easily discover and communicate with each other on a network. However, the lack of proper validation on incoming UPnP requests allows an attacker to send specially crafted packets that can overwhelm the router’s resources, leading to a DoS condition. While specific exploit details are not publicly available (and responsibly withheld to prevent widespread exploitation), the core issue revolves around the router’s inability to handle malformed or excessively large UPnP requests.
CVSS Analysis
Currently, the CVSS score is listed as N/A. However, given the potential for unauthenticated remote denial of service, a CVSS score should be calculated based on the following considerations:
- Attack Vector (AV): Adjacent Network (A) – As the attack requires the attacker to be on the same network.
- Attack Complexity (AC): Low (L) – Easy to exploit.
- Privileges Required (PR): None (N) – No authentication is required.
- User Interaction (UI): None (N) – No user interaction is required.
- Scope (S): Unchanged (U) – The vulnerability affects the router itself.
- Confidentiality Impact (C): None (N) – No confidentiality impact.
- Integrity Impact (I): None (N) – No integrity impact.
- Availability Impact (A): High (H) – The router becomes unavailable.
Based on these factors, a probable CVSS v3.0 score would fall in the range of 6.5 – 7.5 (Medium to High Severity) depending on the specific calculation methodology.
Possible Impact
The successful exploitation of CVE-2025-11676 can result in the following:
- Denial of Service: The router becomes unresponsive, preventing all connected devices from accessing the internet.
- Network Disruption: Critical services reliant on internet connectivity will be interrupted.
- Reputational Damage: For businesses using this router, network downtime can lead to loss of productivity and damage to their reputation.
Mitigation or Patch Steps
The primary mitigation for CVE-2025-11676 is to update the router’s firmware to a version that addresses the vulnerability. Follow these steps:
- Check Your Firmware Version: Access your router’s web interface (typically by typing
192.168.0.1or192.168.1.1in your web browser) and locate the firmware version in the system information or status section. - Download the Latest Firmware: Visit the TP-Link support website and download the latest firmware for your specific TL-WR940N V6 hardware version. You can find the latest firmware here: TP-Link TL-WR940N V6 Firmware Downloads. Make sure to download the firmware for your specific hardware version (V6).
- Update the Firmware: Follow the instructions provided by TP-Link to update the firmware. This usually involves uploading the downloaded firmware file through the router’s web interface.
- Consider Disabling UPnP: If a firmware update is not immediately available or feasible, disabling UPnP can mitigate the risk. Note that this may affect the functionality of certain applications that rely on UPnP for port forwarding. Consult the TP-Link FAQ on how to disable UPnP: TP-Link FAQ on Disabling UPnP.
Important: Always back up your router’s configuration before performing a firmware update. Ensure a stable power supply during the update process to avoid bricking the device.
