Advisory ID: cisco-sa-20021004-toll-fraud
For Public Release 2002 October 4 15:30 UTC (GMT)
The predefined restriction tables in Cisco Unity do not block calls to
the international operator. The default configuration only blocks North
American Numbering Plan (NANP) International Direct Dial (IDD) prefixes, or
those prefixes that start with 9 011. Customers may expect that since direct
dial international calls are blocked, it is not possible for users to forward
calls to international numbers, but the loophole of the international operator
is still allowed under the predefined restriction table. This subversion can be
accomplished by anyone inside or outside of a company who is familiar with how
to configure Cisco Unity and has access to a valid system username and
password, which is further compounded by the common existence of the Example
Administrator and Example Subscriber accounts in many installations.
This vulnerability has been documented as CSCdy54570. These issues are
also being referenced in the Mitre CVE as CAN-2002-1189 and
The following products are identified as affected by this
Cisco Unity software versions 3.1.5 and lower including all 2.x
Unless explicitly stated otherwise, all other Cisco products are not
A workaround exists for this vulnerability which is detailed in the
Workarounds section below.
This advisory is available at
This section provides details on affected products.
Cisco Unity software versions 3.1.5 and lower including all 2.x
No other Cisco products are currently known to be affected by these
The predefined restriction tables in Cisco Unity are for North American
dial plans and do not block calls to the international operator. The default
configuration only blocks IDD patterns that start with 9 011. This may pose a
problem because subscribers can configure call forwarding in Cisco Unity to
point to the international operator (9 00) and then place international calls.
After installing Unity, customers often ignore the Example
Administrator and Example Subscriber accounts. These can be exploited by
dialing into Cisco Unity, logging into the accounts with the default extension
and password, and configuring it to call forward to the international operator
or other toll number.
Two other scenarios in which this could happen are:
Internal users can set their own Cisco Unity mailboxes to forward to
international numbers or toll numbers.
External callers could log into a poorly password protected mailbox
(for example: password=1234), and forward to international numbers or toll
This vulnerability has been documented as CSCdy54570.
Cisco has provided scores for the vulnerabilities in this advisory based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in this Security Advisory is done in accordance with CVSS version 2.0.
CVSS is a standards-based scoring method that conveys vulnerability severity and helps determine urgency and priority of response.
Cisco has provided a base and temporal score. Customers can then compute environmental scores to assist in determining the impact of the vulnerability in individual networks.
Cisco has provided an FAQ to answer additional questions regarding CVSS at
Cisco has also provided a CVSS calculator to help compute the environmental impact for individual networks at
The predefined restriction tables within the Cisco Unity configuration
allows direct dialing of the international operator or other toll calls which
may not be desired. Due to the existence of well known default user accounts,
successful exploitation of those default accounts or policies allowing weak
passwords on accounts can result in toll fraud which may go unnoticed until the
end of a billing cycle.
The default configuration of Cisco Unity will be modified to disallow
forwarding to the international operator in future versions, however a software
upgrade is not necessary in order to mitigate the vulnerability.
Adding additional dial strings to the restriction tables will prevent
Unity from trying to place a toll call. For example, to block all international
calls as well as toll calls while still retaining the ability to dial locally,
the following restriction table entries might be useful for installations in
In the example above, the first line will match and block all domestic
(US) toll calls. The second line will match and block all international calls
including the international operator. The third line matches and allows local
calls. This line is not necessary if your area does not use local area codes.
The fourth line matches and allows local calls. This or other locally
applicable lines should be applied to all restriction tables. Note that some
locations use 10 digit dialing for non-toll calls. In those locations the
restrictions should allow specific non-toll prefixes while blocking all other
For installations outside of North America where the dial plans vary
from the above example, the restriction table entries will be different.
Information to assist in creating restriction tables can be found in the
section entitled "Restriction Tables" in the Cisco Unity System Administration
In addition, Cisco recommends the protection of the Example
Administrator and the Example Subscriber accounts. These accounts at a minimum
should have their default extension and default password changed. This should
be done as part of tightening the security on your Cisco Unity system. For more
details refer to:
Paper: Best Practices for Cisco Unity 3.0.
It is also possible to remove the Example Administrator and the Example
Subscriber accounts. Care must be taken in removing the Example Administrator
account, as removing it improperly could result in the Cisco Unity server no
longer functioning properly. The process to remove those accounts has been
documented at http://www.cisco.com/warp/public/788/AVVID/remove_example_admin.html.
Other methods of mitigating the risk are:
If Unity is integrated with a Call Manager, adding a route filter to
the route pattern Unity uses to dial to the Public Switched Telephone Network
(PSTN) will prevent calls to the international operator.
Restricting Unity from placing calls to the PSTN if that capability
is not needed.
Apply a good password policy. Refer to the white paper on
Practices for Cisco Unity 3.0 .
Cisco has made free software available to address this vulnerability
for affected customers. Prior to deploying software, customers should consult
their maintenance provider or check the software for feature set compatibility
and known issues specific to their environment.
Customers may only install and expect support for the feature sets they
have purchased. By installing, downloading, accessing or otherwise using such
software upgrades, customers agree to be bound by the terms of Cisco's software
license terms found at
or as otherwise set forth at Cisco.com Downloads at
Do not contact either "email@example.com" or "firstname.lastname@example.org"
for software upgrades.
Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
Customers whose Cisco products are provided or maintained through prior
or existing agreement with third-party support organizations such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for guidance and assistance with the appropriate course of
action in regards to this advisory.
The effectiveness of any workaround or fix is dependent on specific
customer situations such as product mix, network topology, traffic behavior,
and organizational mission. Due to the variety of affected products and
releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.
Customers who purchase direct from Cisco but who do not hold a Cisco
service contract and customers who purchase through third-party vendors but are
unsuccessful at obtaining fixed software through their point of sale should get
their upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC
contacts are as follows.
+1 800 553 2447 (toll free from within North America)
+1 408 526 7209 (toll call from anywhere in the world)
Have your product serial number available and give the URL of this
notice as evidence of your entitlement to a free upgrade. Free upgrades for
non-contract customers must be requested through the TAC.
for additional TAC contact information, including special localized telephone
numbers and instructions and e-mail addresses for use in various
The Cisco PSIRT has been made aware of malicious use of the
vulnerability described in this advisory. Customers are advised to perform the
steps as described in the Workarounds section in order to prevent misuse of
their Cisco Unity servers.
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Users concerned about this problem are encouraged to check the URL
given above for any updates.
Updated to include specific release versions and added CVE
Initial Public Release