CVE-2025-27477
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 · uneditedHeap-based buffer overflow in Windows Telephony Service allows an unauthorized attacker to execute code over a network.
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 confidenceA heap-based buffer overflow vulnerability exists in the Windows Telephony Service that allows an unauthenticated remote attacker to execute arbitrary code by sending specially crafted network packets to the affected service. The vulnerability stems from improper memory handling when processing incoming Telephony API requests.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 10.0.10240.20978< 10.0.14393.7969< 10.0.17763.7136< 10.0.19044.5737< 10.0.19045.5737< 10.0.22621.5189< 10.0.22631.5189< 10.0.26100.3775CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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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Check Windows build versionOpen Command Prompt or PowerShell and run 'winver' or 'systeminfo | findstr /B /C:"OS Version"' to obtain the exact build numberAffected if The build number falls below any of these thresholds: 10.0.10240.20978 (1507), 10.0.14393.7969 (1607), 10.0.17763.7136 (1809), 10.0.19044.5737 (21h2), 10.0.19045.5737 (22h2), 10.0.22621.5189 (11 22h2), 10.0.22631.5189 (11 23h2), 10.0.26100.3775 (11 24h2)
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Verify Telephony Service statusOpen Services console (services.msc) or run 'Get-Service Tapisrv' in PowerShell to check if the Windows Telephony Service is runningAffected if The Tapisrv service is running and set to Automatic or Manual startup
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Check for telephony listening portsRun 'netstat -an | findstr LISTENING' or use PowerShell 'Get-NetTCPConnection -State Listen' to identify ports listening for telephony connectionsAffected if Any telephony-related ports (typically TCP 3389, 5060, or custom telephony ports) are in a LISTENING state on network interfaces
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Confirm Telephony API exposureReview firewall rules with 'netsh advfirewall firewall show rule name=all' or Windows Defender Firewall configuration to verify if telephony ports are allowed through the firewallAffected if Inbound firewall rules permit traffic to telephony service ports from untrusted networks
You are affected if your Windows build version is below the thresholds listed AND the Telephony Service (Tapisrv) is running and exposed on the network.
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.
dbcve · scoped10.0.10240.2097810.0.14393.796910.0.17763.7136
Apply the relevant Microsoft security patch for CVE-2025-27477 to all affected Windows systems and ensure the Windows Telephony Service is updated to a patched version. Consider disabling the Telephony Service if not required, or restricting network access to telephony ports.
Windows 10 1507: 10.0.10240.20978 | Windows 10 1607: 10.0.14393.7969 | Windows 10 1809: 10.0.17763.7136 | Windows 10 21h2: 10.0.19044.5737 | Windows 10 22h2: 10.0.19045.5737 | Windows 11 22h2: 10.0.22621.5189 | Windows 11 23h2: 10.0.22631.5189 | Windows 11 24h2: 10.0.26100.3775
- Open Windows Settings by pressing Win+I
- Navigate to Update & Security > Windows Update
- Click 'Check for updates' to download and install the latest security updates
- If using WSUS or SCCM, approve the relevant monthly cumulative update for your Windows version
- Verify the update installed successfully by checking Windows Update history
- Restart the system if prompted to complete the installation
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-27477 — 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-2025-27477 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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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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