The following client identifier issues can have security implications:

• Ensuring the uniqueness and complexity of the CFToken identifier
• Limiting the availability of Session identifiers

The next sections discuss these issues.

Ensuring CFToken uniqueness and security

By default, ColdFusion uses an eight-digit random number in the CFToken identifier. This CFToken format provides a unique, secure identifier for users under most circumstances. (In ColdFusion, the method for generating this number uses a cryptographic-strength random number generator that is seeded only when the server starts.)

However, in the ColdFusion Administrator, you can enable the Settings page to produce a more complex CFToken identifier. If you enable the Use UUID for cftoken option, ColdFusion creates the CFToken value by prepending a 16-digit random hexadecimal number to a ColdFusion UUID. The resulting CFToken identifier looks similar to the following:

3ee6c307a7278c7b-5278BEA6-1030-C351-3E33390F2EAD02B9

Providing Session security

ColdFusion uses the same client identifiers for the Client scope and the standard Session scope. Because the CFToken and CFID values are used to identify a client over a period of time, they are normally saved as cookies on the user's browser. These cookies persist until the client's browser deletes them, which can be a considerable length of time. As a result, hackers could have more access to these variables than if ColdFusion used different user identifiers for each session.

A hacker who has the user's CFToken and CFID cookies could gain access to user data by accessing a web page during the user's session using the stolen CFToken and CFID cookies. While this scenario is unlikely, it is theoretically possible.

You can remove this vulnerability by selecting the Use J2EE Session Variables option on the ColdFusion Administrator Memory Variables page. The J2EE session management mechanism creates a new session identifier for each session, and does not use either the CFToken or the CFID cookie value.