CVE-2026-12221 Yealink SIP-T46U Firmware Chunk Upload upgrade sprintf stack-based overflow
A stack-based buffer overflow in the firmware chunk upload handler allows local network attackers to execute arbitrary code on Yealink SIP-T46U devices.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-12221?
CVE-2026-12221 is a high-severity memory corruption vulnerability in Yealink SIP-T46U, published on 15 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-12221?
How do I fix CVE-2026-12221?
No fix has been published for CVE-2026-12221 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-12221 being exploited?
There is no known exploitation of CVE-2026-12221 in the wild and no public exploit code.
Sources
Also known as GHSA-3x75-g3h6-5r8m.