CVE-2026-12220 | Yealink SIP-T46U 108.86.0.118 Firmware Chunk Upload handler accupgradebychunk mod_upgrade.SparePartsUpload uid stack-based overflow

A vulnerability, which was classified as critical, was found in Yealink SIP-T46U 108.86.0.118. This affects the function mod_upgrade.SparePartsUpload of the file /api/upgrade/accupgradebychunk of the component Firmware Chunk Upload handler. Such manipulation of the argument uid leads to stack-based buffer overflow.

This vulnerability is uniquely identified as CVE-2026-12220. The attack can only be initiated within the local network. Moreover, an exploit is present.

The vendor was contacted early about this disclosure but did not respond in any way.