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Description
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.
Modes of Introduction:
– Architecture and Design
Related Weaknesses
CWE-340
Consequences
Other: Varies by Context
This weakness could be exploited by an attacker in a number ways depending on the context. If a predictable number is used to generate IDs or keys that are used within protection mechanisms, then an attacker could gain unauthorized access to the system. If predictable filenames are used for storing sensitive information, then an attacker might gain access to the system and may be able to gain access to the information in the file.
Potential Mitigations
Phase: Implementation
Description:
Increase the entropy used to seed a PRNG.
Phase: Architecture and Design, Requirements
Description:
Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C (“Approved Random Number Generators”).
Phase: Implementation
Description:
Use a PRNG that periodically re-seeds itself using input from high-quality sources, such as hardware devices with high entropy. However, do not re-seed too frequently, or else the entropy source might block.
CVE References
- CVE-2002-0389
- Mail server stores private mail messages with predictable filenames in a world-executable directory, which allows local users to read private mailing list archives.
- CVE-2001-1141
- PRNG allows attackers to use the output of small PRNG requests to determine the internal state information, which could be used by attackers to predict future pseudo-random numbers.
- CVE-2000-0335
- DNS resolver library uses predictable IDs, which allows a local attacker to spoof DNS query results.
- CVE-2005-1636
- MFV. predictable filename and insecure permissions allows file modification to execute SQL queries.
