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AUSCERT External Security Bulletin Redistribution
Cisco IP Phones Web Server Remote Code Execution and Denial
of Service Vulnerability
17 April 2020
AusCERT Security Bulletin Summary
Product: IP Phone 78xx Desktop Phones
IP Phone 88xx Desktop Phones
Unified IP Conference Phone 8831
Wireless IP Phone 8821 and 8821-EX
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Root Compromise -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2020-3161
Revision History: April 17 2020: Exploitation and public announcements has been updated,
as there is now public exploit code.
April 16 2020: Initial Release
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Cisco IP Phones Web Server Remote Code Execution and Denial of Service
Advisory ID: cisco-sa-voip-phones-rce-dos-rB6EeRXs
First Published: 2020 April 15 16:00 GMT
Last Updated: 2020 April 16 15:57 GMT
Version 1.1: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCuz03016CSCvs78272CSCvs78441
o A vulnerability in the web server for Cisco IP Phones could allow an
unauthenticated, remote attacker to execute code with root privileges or
cause a reload of an affected IP phone, resulting in a denial of service
The vulnerability is due to a lack of proper input validation of HTTP
requests. An attacker could exploit this vulnerability by sending a crafted
HTTP request to the web server of a targeted device. A successful exploit
could allow the attacker to remotely execute code with root privileges or
cause a reload of an affected IP phone, resulting in a DoS condition.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
This advisory is available at the following link:
o Vulnerable Products
This vulnerability affects the following Cisco products if they have web
access enabled and are running a firmware release earlier than the first
fixed release for that device:
IP Phone 7811, 7821, 7841, and 7861 Desktop Phones
IP Phone 8811, 8841, 8845, 8851, 8861, and 8865 Desktop Phones
Unified IP Conference Phone 8831
Wireless IP Phone 8821 and 8821-EX
Note: Web access is disabled by default. Administrators can check the web
access configuration from Cisco Unified Communications Manager by choosing
Device > Phone > Select a Phone and checking whether Web Access is set to
Enabled or Disabled . If it is set to Disabled , the IP phone is not
For information about which Cisco firmware releases are vulnerable, see the
Fixed Software section of this advisory.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following
ATA 190 Analog Telephone Adapter
ATA 191 Analog Telephone Adapter
ATA 192 Multiplatform Analog Telephone Adapter
IP Conference Phone 7832
IP Conference Phone 7832 with Multiplatform Firmware
IP Conference Phone 8832
IP Conference Phone 8832 with Multiplatform Firmware
IP DECT 6825 with Multiplatform Firmware
IP Phone 6821, 6841, 6851, 6861, and 6871 with Multiplatform Firmware
IP Phone 7811, 7821, 7841, and 7861 Desktop Phones with Multiplatform
IP Phone 8811, 8841, 8845, 8851, 8861, and 8865 Desktop Phones with
SPA112 2-Port Phone Adapter
SPA122 ATA with Router
SPA2102 Phone Adapter with Router
SPA232D Multi-Line DECT ATA
SPA3102 Voice Gateway with Router
SPA8000 8-Port IP Telephony Gateway
SPA8800 IP Telephony Gateway with 4 FXS and 4 FXO Ports
Small Business SPA300 Series IP Phones
Small Business SPA500 Series IP Phones
Unified IP Conference Phone 8831 for Third-Party Call Control
Unified IP Phone 6901 and 6911
Unified SIP Phone 3905
o There are no workarounds that address this vulnerability.
However, if web access is not required, disabling it is considered a
mitigation for this vulnerability. If web access is disabled, the phone is
not vulnerable. For additional information, see the Web Access Disable
chapter of the Phone Hardening guide.
Note: Web access is disabled by default on Cisco IP phones.
o Cisco has released free software updates that address the vulnerability
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license: https://www.cisco.com/c/en/us/products/
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories and Alerts page , to determine exposure and a
complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
Customers are advised to upgrade to an appropriate fixed firmware release
as indicated in the following table:
Cisco IP Phone Model Cisco Bug First Fixed
IP Phone 7811, 7821, 7841, 7861 Desktop Phones CSCuz03016 11.7(1)
IP Phone 8811, 8841, 8845, 8851, 8861, 8865 CSCuz03016 11.7(1)
Unified IP Conference Phone 8831 CSCvs78441 10.3(1)SR6
Wireless IP Phone 8821, 8821-EX CSCvs78272 11.0(5)SR3
To download the Cisco IP Phone firmware from the Software Center on
Cisco.com , do the following:
1. Click Browse all .
2. Choose Collaboration Endpoints > IP Phones .
3. Choose a specific product from the right pane of the product selector.
4. Choose a release from the left pane of the product page.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is aware that
proof-of-concept exploit code is available for the vulnerability described
in this advisory.
o This vulnerability was found during internal security testing. Cisco would
also like to thank Jacob Baines of Tenable for reporting this
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
| Version | Description | Section | Status | Date |
| | Updated Exploitation | | | |
| | and Public | Exploitation | | |
| 1.1 | Announcements to | and Public | Final | 2020-APR-16 |
| | indicate that there is | Announcements | | |
| | public exploit code. | | | |
| 1.0 | Initial public | - | Final | 2020-APR-15 |
| | release. | | | |
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