Security Advisory: Pre-Authentication Stack-based Buffer Overflow Remote Code Execution in TDDPv2 Subtype 0x91 on Deco M9 Plus (CVE-2026-8618)

Vulnerability and Impact Description:

CVE-2026-8618: Pre-Authentication Stack-based Buffer Overflow Remote Code Execution in TDDPv2 Subtype 0x91 on Deco M9 Plus

A stack-based buffer overflow vulnerability exists in the TDDPv2 service (/usr/bin/tddp) on Deco M9 Plus due to insufficient validation of decrypted request data length before it is copied into a fixed-size stack buffer in the subtype 0x91 handler.

Successful exploitation may allow an adjacent, unauthenticated attacker to cause a denial of service or achieve arbitrary code execution during the device setup phase through crafted TDDP packets.

CVSS v4.0 Score: 7.7 / High

CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L

Affected Products/Versions and Fixes:

Recommendations:

We strongly recommend that users with affected devices take the following actions:

1. Update affected devices to the latest firmware version that fixed the vulnerability:

EN: Download for Deco M9 Plus | TP-Link

US: Download for Deco M9 Plus | TP-Link

Disclaimer:

This advisory is provided for informational purposes only and is subject to change without notice. The information is provided “as is” without warranties of any kind. TP-Link recommends that customers promptly apply available firmware updates or implement documented workarounds as provided in this advisory. Devices/systems that are not updated or mitigated as described may remain vulnerable, and TP-Link disclaims any responsibility or liability for any damages or losses arising from a failure to implement such updates.