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Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-334: Small Space of Random Values

Weakness ID: 334
Abstraction: Base
Status: Draft
Presentation Filter:
+ Description

Description Summary

The number of possible random values is smaller than needed by the product, making it more susceptible to brute force attacks.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms

Languages

All

+ Common Consequences
ScopeEffect
Access Control
Other

Technical Impact: Bypass protection mechanism; Other

An attacker could easily guess the values used. This could lead to unauthorized access to a system if the seed is used for authentication and authorization.

+ Demonstrative Examples

Example 1

The following XML example code is a deployment descriptor for a Java web application deployed on a Sun Java Application Server. This deployment descriptor includes a session configuration property for configuring the session ID length.

(Bad Code)
Example Language: XML 
<sun-web-app>
...
<session-config>
<session-properties>
<property name="idLengthBytes" value="8">
<description>The number of bytes in this web module's session ID.</description>
</property>
</session-properties>
</session-config>
...
</sun-web-app>

This deployment descriptor has set the session ID length for this Java web application to 8 bytes (or 64 bits). The session ID length for Java web applications should be set to 16 bytes (128 bits) to prevent attackers from guessing and/or stealing a session ID and taking over a user's session.

Note for most application servers including the Sun Java Application Server the session ID length is by default set to 128 bits and should not be changed. And for many application servers the session ID length cannot be changed from this default setting. Check your application server documentation for the session ID length default setting and configuration options to ensure that the session ID length is set to 128 bits.

+ Observed Examples
ReferenceDescription
Product uses 5 alphanumeric characters for filenames of expense claim reports, stored under web root.
Product uses small number of random numbers for a code to approve an action, and also uses predictable new user IDs, allowing attackers to hijack new accounts.
SYN cookies implementation only uses 32-bit keys, making it easier to brute force ISN.
Complex predictability / randomness (reduced space).
+ Potential Mitigations

Phases: Architecture and Design; Requirements

Strategy: Libraries or Frameworks

Use products or modules that conform to FIPS 140-2 [R.334.1] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators").

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class330Use of Insufficiently Random Values
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfCategoryCategory905SFP Primary Cluster: Predictability
Software Fault Pattern (SFP) Clusters (primary)888
ParentOfWeakness VariantWeakness Variant6J2EE Misconfiguration: Insufficient Session-ID Length
Research Concepts (primary)1000
MemberOfViewView884CWE Cross-section
CWE Cross-section (primary)884
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERSmall Space of Random Values
+ References
[R.334.1] [REF-1] Information Technology Laboratory, National Institute of Standards and Technology. "SECURITY REQUIREMENTS FOR CRYPTOGRAPHIC MODULES". 2001-05-25. <http://csrc.nist.gov/publications/fips/fips140-2/fips1402.pdf>.
[R.334.2] [REF-17] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 20: Weak Random Numbers." Page 299. McGraw-Hill. 2010.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time_of_Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings
2009-03-10CWE Content TeamMITREInternal
updated Potential_Mitigations
2009-12-28CWE Content TeamMITREInternal
updated Potential_Mitigations
2010-06-21CWE Content TeamMITREInternal
updated Potential_Mitigations
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-09-13CWE Content TeamMITREInternal
updated Potential_Mitigations, References
2012-05-11CWE Content TeamMITREInternal
updated Common_Consequences, Demonstrative_Examples, References, Relationships
2012-10-30CWE Content TeamMITREInternal
updated Potential_Mitigations

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Page Last Updated: January 18, 2017