CVE-2026-12220
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA vulnerability has been found in Yealink SIP-T46U 108.86.0.118. This affects the function mod_upgrade.SparePartsUpload of the file /api/upgrade/accupgradebychunk of the component Firmware Chunk Upload handler. Such manipulation of the argument uid leads to stack-based buffer overflow. The attack can only be initiated within the local network. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure and is working on a patch to fix it.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceStack-based buffer overflow in Yealink SIP-T46U firmware chunk upload handler (mod_upgrade.SparePartsUpload in /api/upgrade/accupgradebychunk). The uid parameter is not properly bounds-checked, allowing local network attackers to overflow the stack and potentially execute arbitrary code.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Adjacent
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the Yealink SIP-T46U deviceAccess the device web interface or check the device label/menu for model number confirmation. The SIP-T46U is a desk IP phone commonly used in enterprise environments.Affected if The device model is Yealink SIP-T46U
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Check the installed firmware versionLog into the phone web interface (usually via HTTP/HTTPS on the device IP), navigate to Status or Settings > Device page, and locate the firmware version field. Alternatively, access the phone menu on the device display under Status > Phone. Compare the version to 108.86.0.118.Affected if Firmware version is 108.86.0.118 exactly (the specific affected version)
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Verify the web API endpoint is accessibleFrom a machine on the same local network as the phone, attempt to access the device management interface by browsing to the device IP address. Check if the /api/upgrade/accupgradebychunk endpoint responds (note: direct access to this internal API endpoint may not return a readable response).Affected if The device web management interface is reachable from the local network without authentication restrictions
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Confirm network accessibility of the management interfaceFrom a host on the local network, verify the device IP is reachable via ping and check if ports 80 or 443 (HTTP/HTTPS) are open on the device using a port scanner or telnet/nc commands.Affected if The device management web interface is exposed to the local network without network segmentation or access controls
A user is affected if they have a Yealink SIP-T46U device running firmware version 108.86.0.118 with the web management interface accessible from the local network, since the exploit requires local network access to reach the vulnerable /api/upgrade/accupgradebychunk endpoint.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataRestrict network access to the device's management interface to trusted local users only; isolate the device on a separate VLAN segment; monitor for exploit attempts; apply vendor firmware patch when available.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-12220 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-12220 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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