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CVE-2026-12221 Yealink CVE debrief

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 but did not respond in any way.

Vendor
Yealink
Product
SIP-T46U
CVSS
HIGH 7.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-15
Original CVE updated
2026-06-27
Advisory published
2026-06-15
Advisory updated
2026-06-27

Who should care

Users of Yealink SIP-T46U 108.86.0.118 within local networks are at risk due to the potential for stack-based buffer overflow attacks.

Technical summary

The vulnerability, CVE-2026-12221, is a stack-based buffer overflow issue (CWE-119, CWE-121) in the Firmware Chunk Upload Handler of Yealink SIP-T46U 108.86.0.118. It has a CVSS score of 7.3 and is considered HIGH severity.

Defensive priority

High

Recommended defensive actions

  • Apply patches or updates provided by the vendor as soon as available.
  • Limit access to the Firmware Chunk Upload Handler to only necessary personnel.
  • Monitor network traffic for suspicious activity related to the Yealink SIP-T46U device.

Evidence notes

The CVE record was published and modified on 2026-06-15T06:16:24.263Z. The vulnerability details were obtained from the NVD and CVE.org.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-12221 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-12221

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-12221 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-12221

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.