Stack-based Buffer Overflow in Yealink SIP-T46U Firmware Chunk Upload Handler
CVE-2026-12221 is a stack-based buffer overflow affecting Yealink SIP-T46U devices running firmware version 108.86.0.118. The flaw is reported in the Firmware Chunk Upload Handler exposed via /api/upgrade/upgrade. According to the provided content, the vulnerable code path involves the use of sprintf, and crafted manipulation of the uid/start_offset argument can overflow a stack buffer. The issue is reachable from within the local network, and a public exploit has reportedly been disclosed.
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Exploits
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No public exploit code observed for this vulnerability.
Recent activity
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.