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CVE-2026-6242: Authenticated Format String Vulnerability in ONVIF Subscribe Service on TP-Link Tapo C520WS

• Severity: medium (CVSS 6.8 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-06 · updated 2026-07-23
• Weakness: CWE-134

Description

An authenticated format string vulnerability exists in the ONVIF Subscribe service in Tapo C520WS v2 due to improper handling of externally supplied parameters within formatting functions. An attacker may inject crafted format strings into event subscription requests or notification generation path to disrupt normal service execution. Successful exploitation may cause the event notification service to terminate unexpectedly, resulting in the loss of real-time alarm functionality and disruption of event notifications.

Affected products

• TP-Link Systems Inc. Tapo C520WS v2: before 1.2.6 Build 260528 — fixed in 1.2.6 Build 260528

How to fix

Upgrade to a fixed version: TP-Link Systems Inc. Tapo C520WS v2 1.2.6 Build 260528. Check the vendor advisory for mitigations.

References

• https://www.tp-link.com/en/support/download/tapo-c520ws/#Firmware-Release-Notes
• https://www.tp-link.com/us/support/download/tapo-c520ws/#Firmware-Release-Notes
• https://www.tp-link.com/us/support/faq/5120/

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