Desk Phone 9871 FirmwareOperating system · Cisco
CVE-2025-20350
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 in the web UI of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 running Cisco SIP Software could allow an unauthenticated, remote attacker to cause a DoS condition on an affected device. This vulnerability is due to a buffer overflow when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending crafted HTTP input to the device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. Note: To exploit this vulnerability, the phone must be registered to Cisco Unified Communications Manager and have Web Access enabled. Web Access is disabled by default.
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 confidenceBuffer overflow vulnerability in the web UI of Cisco Desk Phone 9800 Series, Cisco IP Phone 7800/8800 Series, and Cisco Video Phone 8875 running Cisco SIP Software. An unauthenticated remote attacker can send crafted HTTP packets to trigger the overflow, causing the affected device to reload and result in a denial of service condition.
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
Desk Phone 9871 FirmwareOperating system
>= 3.0\(1\), <= 3.2\(1\)
Desk Phone 9841 FirmwareOperating system
>= 3.0\(1\), <= 3.2\(1\)
Desk Phone 9851 FirmwareOperating system
>= 3.0\(1\), <= 3.2\(1\)
Desk Phone 9861 FirmwareOperating system
>= 3.0\(1\), <= 3.2\(1\)
Ip Phone 8865 FirmwareOperating system
< 14.3\(1\)= 14.3\(1\)
Ip Phone 7811 FirmwareOperating system
< 14.3\(1\)= 14.3\(1\)
Ip Phone 7821 FirmwareOperating system
< 14.3\(1\)= 14.3\(1\)
Ip Phone 7841 FirmwareOperating system
< 14.3\(1\)= 14.3\(1\)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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 phone modelAccess the phone's web UI or check the device label/menu to determine the exact model (e.g., Cisco IP Phone 7811, Cisco Desk Phone 9851, etc.)Affected if Model is one of: Cisco Desk Phone 9871, 9841, 9851, 9861, Cisco IP Phone 8865, 7811, 7821, or 7841
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Check the installed firmware versionNavigate to the phone's web UI (if enabled) and look for the firmware version in the device info or status page, or access the phone menu to find the firmware versionAffected if Firmware version falls within: 3.0(1) to 3.2(1) inclusive for Desk Phone models 9841/9851/9861/9871; OR version is 14.3(1) or earlier for IP Phone models 7811/7821/7841/8865
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Verify if Web Access is enabledCheck the phone's web UI settings or the web server configuration. On the phone, go to Settings > Web Server or similar, or attempt to access the phone's IP address via HTTP to see if a login prompt appearsAffected if Web Access/Server is enabled on the device (required for exploitation - note that web access is disabled by default)
Device is affected only if it is a listed phone model, runs an affected firmware version within the specified ranges, AND has Web Access enabled (web access must be explicitly turned on for the vulnerability to be exploitable).
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 data14.3
Disable Web Access on affected phones if not required, as it is disabled by default and required for exploitation. Apply Cisco's available software updates/patches for Cisco SIP Software when released to address the buffer overflow vulnerability.
Fix this in Desk Phone 9871 Firmware
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-20350 — 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-2025-20350 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
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