# CVE-2026-12220: Yealink SIP-T46U stack overflow in Firmware Chunk Upload handler

Source: https://junglewise.ai/threats/cve-2026-12220-yealink-sip-t46u-stack-overflow-in-firmware-chunk-upload-handler  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-15. Updated: 2026-06-15  
License: CC BY 4.0 with a link back

CVE-2026-12220 · Severity: high · CVSS 8 · Published 2026-06-15

A security vulnerability exists in Yealink SIP-T46U business desk phones. An attacker on the same local network could exploit this flaw to crash the device or potentially take control of it. This could lead to a disruption of communication services or unauthorized access to the device's functions.

Technologies: [Yealink SIP-T46U](https://junglewise.ai/threats/technologies/sip-t46u). Vendors: [Yealink](https://junglewise.ai/threats/vendors/yealink).

## Quick answers

**Is CVE-2026-12220 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-12220 being exploited in the wild.

**How severe is CVE-2026-12220?** High severity, with a CVSS score of 8, published 15 June 2026.

**Which products and versions are affected?** Yealink SIP-T46U 108.86.0.118.

**Is there a fix for CVE-2026-12220?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-12220 attacked?** It is attacked from the adjacent network, in an operating system.

**Am I affected by CVE-2026-12220?** Check whether you run Yealink SIP-T46U at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stack-based buffer overflow vulnerability exists in the Yealink SIP-T46U firmware version 108.86.0.118. The flaw is located within the mod_upgrade.SparePartsUpload function in the /api/upgrade/accupgradebychunk component. By manipulating the 'uid' argument during a firmware chunk upload request, an attacker with low-privileged access on the adjacent network can trigger the overflow. This can lead to arbitrary code execution or a complete system crash. As of the advisory date, the vendor has not responded to the disclosure, and no official patch is confirmed.

## Affected products

- Yealink SIP-T46U 108.86.0.118

## Timeline

- 2026-06-15: disclosed: Public disclosure of the vulnerability and exploit details.
- 2026-06-15: advisory

## References

- [http://cdn2.v50to.cc/T46U/T46U_mod_upgrade_SparePartsUpload_stack_overflow.zip](http://cdn2.v50to.cc/T46U/T46U_mod_upgrade_SparePartsUpload_stack_overflow.zip)
- [https://vuldb.com/cve/CVE-2026-12220](https://vuldb.com/cve/CVE-2026-12220)
- [https://vuldb.com/submit/834205](https://vuldb.com/submit/834205)
- [https://vuldb.com/vuln/370863](https://vuldb.com/vuln/370863)
- [https://vuldb.com/vuln/370863/cti](https://vuldb.com/vuln/370863/cti)

## Related threats

- [Yealink SIP-T46U command injection in Web FastCGI Service](https://junglewise.ai/threats/cve-2026-12223-yealink-sip-t46u-command-injection-in-web-fastcgi-service)
- [Yealink SIP-T46U stack buffer overflow in Web FastCGI Service](https://junglewise.ai/threats/cve-2026-12222-yealink-sip-t46u-stack-buffer-overflow-in-web-fastcgi-service)
- [Yealink SIP-T46U stack-based buffer overflow in Firmware Chunk Upload Handler](https://junglewise.ai/threats/cve-2026-12221-yealink-sip-t46u-stack-based-buffer-overflow-in-firmware-chunk)
- [Yealink SIP-T46U command injection in Web FastCGI Service](https://junglewise.ai/threats/cve-2026-12219-yealink-sip-t46u-command-injection-in-web-fastcgi-service)
- [Yealink SIP-T46U stack-based buffer overflow in Web FastCGI Service](https://junglewise.ai/threats/cve-2026-12218-yealink-sip-t46u-stack-based-buffer-overflow-in-web-fastcgi)