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Severity
Critical
Title
Nortel UNIStim IT Sequence Number Intercept
Description

UNIStim is the proprietary protocol used for signaling within a Nortel PBX environment. The protocol includes the ability to change from one legitimate server to another.

 

However, an attacker could take advantage of this by using a series of two commands to assume control of a UNIStim client.  A simple sniffing or brute force attack is required to determine the correct sequence number to use in the issuing of the new commands, causing a Denial of Service, etc.

Details
Category
Unauthorized Access
Vendor
Nortel
Product
UNIStim Clients and Servers
Released
2008-04-01
updated
2008-04-01
Response
Patch available
Recommendations

To completely address the issue requires implementing the secure version of UNIStim, which in turn may require a proxy system for the server as well as additional administration effort. In the short term it is recommended that a VoIP aware IPS product, such as VoIPguard, with signatures to detect attempts to exploit this issue, be implemented to prevent it from being exploited. Implementing best practices can limit the exposure of this issue.  Therefore it is recommended that only authorized systems and users be allowed to communicate using UNIStim and that appropriate access be implemented on network switches.

 

Nortel customers with a valid support agreement may wish to speak with their support contact in order to obtain further vendor details.

Tracking Id
VSRNT-2008-002
 

Each line represents an individual vulnerability or group of vulnerabilities. For example, "UCM Multiple Hardcoded Passwords" is presented here in a single line but was reported to Nortel as sixteen (16) individual vulnerabilities.

Severity Legend

Click on a level for description
Low

A low severity issue falls into one of two categories.  Firstly, there are those that are not directly exploitable and affect a single IP client, a small subset of the deployment, or are quite innocuous taken by themselves. In other words, they provide information which either involves only a small number (or single) client and that information requires considerable other information or effort to be useful to an attacker.  The other category of low severity issues includes those that are best practices which are not intended to directly mitigate an exploitable risk but to increase overall security robustness and demonstrate due diligence.

Medium

A medium severity issue is typically an issue which can lead to further exploitation or provides short-lived effect on a minimal number of clients.  It may not be immediately exploitable but provides sufficient information or access to move an attack closer to fruition.  Alternately it may provide unauthorized access not directly related to the VoIP portion of the network.

High

A high severity issue can be exploited to compromise one or more nodes within the deployment but may require authentication, especially when exploiting multiple systems simultaneously. In addition, it may be possible to protect against untrusted exploitation of the issue by deploying traditional security tools.

Critical

A critical severity issue can be exploited by an untrusted individual to compromise the entire deployment under review.  There are no security or protective mechanisms in place that will mediate exploitation of this vulnerability by an untrusted individual.

Vendor Response Legend

Patch available
Workaround proposed
Attempting to address the issue
No vendor response
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