CVE-2026-76649 in TL-WR841N
Summary
by MITRE • 08/29/2026
A NULL pointer dereference vulnerability exists in TL-WR841N v14 in the UPnP service when processing SOAP action requests. A specially crafted SOAP action request containing unexpected XML content may cause the UPnP daemon to terminate unexpectedly.
Successful exploitation may result in a denial-of-service condition affecting UPnP functionality until the service is restarted or the device is rebooted.
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Analysis
by VulDB Data Team • 08/29/2026
The vulnerability identified in TP-Link TL-WR841N v14 routers stems from an improper handling of input data within the Universal Plug and Play (UPnP) service, specifically during the processing of Simple Object Access Protocol SOAP action requests. This flaw is classified as a NULL pointer dereference, which corresponds to CWE-476 in the Common Weakness Enumeration taxonomy. The root cause lies in the application's failure to adequately validate or check pointers before they are accessed within the XML parsing logic. When the UPnP daemon receives a specially crafted SOAP request containing unexpected or malformed XML content, it attempts to dereference a pointer that has not been properly initialized or has become invalid due to prior processing errors. This lack of defensive programming leads directly to an access violation where the software tries to read from memory address zero, triggering a critical fault in the operating system's kernel protection mechanisms.
From an operational perspective, this technical flaw results in immediate and severe availability impacts for the affected device. Upon receiving the malicious payload, the UPnP daemon terminates unexpectedly rather than gracefully handling the error or returning a standard SOAP fault response. This abrupt termination disrupts all network address translation port mapping services managed by the daemon, effectively rendering any applications relying on automatic port forwarding non-functional until the service is manually restarted or the entire router hardware is rebooted. For home and small office networks that depend heavily on UPnP for seamless connectivity of gaming consoles, video conferencing tools, or IoT devices, this denial-of-service condition can cause significant operational disruption without requiring complex exploitation techniques beyond sending a single malformed HTTP POST request to the appropriate SOAP endpoint.
The attack vector is particularly concerning because it allows for remote code execution in terms of service disruption with no authentication required if UPnP is enabled and accessible from the local network or potentially through NAT traversal depending on firewall configurations. This aligns with MITRE ATT&CK technique T1498, Network Denial of Service, specifically noting that this vulnerability enables resource exhaustion via a single targeted action rather than sustained traffic flooding. The simplicity of the exploit means that automated scanning tools can easily identify vulnerable devices by sending test payloads and observing for service crashes or HTTP 500 errors indicative of internal server faults caused by the crash.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Users should immediately disable UPnP functionality within the router's administrative interface if it is not strictly necessary, as this removes the attack surface entirely since the vulnerable code path will no longer be invoked. If UPnP is required for specific applications, administrators should ensure that firmware updates provided by TP-Link are applied promptly once available to patch the underlying C/C++ memory management error. Furthermore, network segmentation can help limit exposure; placing IoT devices and other critical endpoints in a separate VLAN restricts potential attackers from reaching the router's internal UPnP service even if they gain initial access to the local network segment. Implementing strict input validation at the application layer is also essential for future development cycles to prevent similar NULL pointer dereferences by ensuring all pointers are verified against null values before use, adhering to secure coding standards such as those outlined in OWASP guidelines for memory safety and error handling.