This vulnerability (CVE-2026-6242) affects the ONVIF Subscribe service in TP-Link Tapo C520WS v2 devices. It is a format string vulnerability (CWE-134) caused by improper handling of externally supplied parameters within formatting functions. An authenticated attacker can inject crafted format strings into event subscription requests or the notification generation path. Successful exploitation results in termination of the event notification service, disrupting real-time alarm and event notification functionality. The CVSS 4.0 base score is 6.8 (medium severity), with attack vector being adjacent network, low attack complexity, no user interaction, and high privileges required. No patch or remediation level has been disclosed by the vendor as of the publication date.

Exploitation causes the event notification service on the affected device to terminate unexpectedly. This results in loss of real-time alarm functionality and disruption of event notifications, potentially impacting monitoring and response capabilities dependent on these alerts.

No official patch or remediation has been disclosed by the vendor at this time. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since the vulnerability requires authenticated access and high privileges, restricting access to trusted users and networks may reduce risk until a fix is available.