CVE-2026-12221: Yealink SIP-T46U Firmware Chunk Upload upgrade sprintf stack-based overflow

Severity: high (CVSS 8.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-15 · updated 2026-07-24
Weakness: CWE-119

Description

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 and is working on a patch to fix it.

Affected products

Yealink SIP-T46U: 108.86.0.118

References

http://cdn2.v50to.cc/T46U/T46U_mod_upgrade_Upgrade_chunk_stack_overflow.zip
https://vuldb.com/cve/CVE-2026-12221
https://vuldb.com/submit/834207
https://vuldb.com/vuln/370864
https://vuldb.com/vuln/370864/cti

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