CVE-2026-12221 is a high-severity vulnerability (CVSS 8).
Summary
A vulnerability was found in Yealink SIP-T46U 108.86.0.118. This impacts the function sprintf of the file /api/upgrade/upgrade of the component Firmware Chunk Upload Handler. Performing a manipulation of the argument uid/start_offset results in stack-based buffer overflow. The attack needs to be approached within the local network. The exploit has been made public and could be used. The vendor was contacted early about this disclosure but did not respond in any way.
Remediation
Apply the vendor’s update during your next patch window and verify exposure. Patch-management tools that can deploy and verify the fix include Action1, Automox, ManageEngine Patch Manager Plus, ManageEngine Endpoint Central. See our best patch management ranking.