Predictable from Observable State
A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.
Demonstrations
The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.
Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.
Example One
This code generates a unique random identifier for a user's session.
function generateSessionID($userID){
srand($userID);
return rand();
}Because the seed for the PRNG is always the user's ID, the session ID will always be the same. An attacker could thus predict any user's session ID and potentially hijack the session.
This example also exhibits a Small Seed Space (CWE-339).
See Also
Weaknesses in this category are related to randomness.
Weaknesses in this category are related to the "Frail Security in Protocols" category from the SEI ETF "Categories of Security Vulnerabilities in ICS" as published in ...
Weaknesses in this category are related to a software system's random number generation.
This view (slice) covers all the elements in CWE.
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This view contains a selection of weaknesses that represent the variety of weaknesses that are captured in CWE, at a level of abstraction that is likely to be useful t...
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