CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

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ID

CWE-333: Improper Handling of Insufficient Entropy in TRNG

Weakness ID: 333
Abstraction: Variant
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
True random number generators (TRNG) generally have a limited source of entropy and therefore can fail or block.
+ Extended Description
The rate at which true random numbers can be generated is limited. It is important that one uses them only when they are needed for security.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More general than a Base weakness.703Improper Check or Handling of Exceptional Conditions
ChildOfBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.331Insufficient Entropy
+ Relevant to the view "Architectural Concepts" (CWE-1008)
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.1013Encrypt Data
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
ChildOfBaseBase - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.331Insufficient Entropy
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
ImplementationREALIZATION: This weakness is caused during implementation of an architectural security tactic.
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Language-Independent (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Availability

Technical Impact: DoS: Crash, Exit, or Restart

A program may crash or block if it runs out of random numbers.
+ Likelihood Of Exploit
Low
+ Demonstrative Examples

Example 1

This code uses a TRNG to generate a unique session id for new connections to a server:

(bad code)
Example Language:
while (1){
if (haveNewConnection()){
if (hwRandom()){
int sessionID = hwRandom();
createNewConnection(sessionID);
} } }

This code does not attempt to limit the number of new connections or make sure the TRNG can successfully generate a new random number. An attacker may be able to create many new connections and exhaust the entropy of the TRNG. The TRNG may then block and cause the program to crash or hang.

+ Potential Mitigations

Phase: Implementation

Rather than failing on a lack of random numbers, it is often preferable to wait for more numbers to be created.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.861CERT Java Secure Coding Section 49 - Miscellaneous (MSC)
MemberOfCategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic.905SFP Primary Cluster: Predictability
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPFailure of TRNG
CERT Java Secure CodingMSC02-JGenerate strong random numbers
+ Content History
Submissions
Submission DateSubmitterOrganization
CLASP
Modifications
Modification DateModifierOrganization
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2009-05-27CWE Content TeamMITRE
updated Description, Name
2009-10-29CWE Content TeamMITRE
updated Description, Other_Notes
2011-06-01CWE Content TeamMITRE
updated Common_Consequences, Relationships, Taxonomy_Mappings
2012-05-11CWE Content TeamMITRE
updated Relationships
2012-10-30CWE Content TeamMITRE
updated Demonstrative_Examples
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Likelihood_of_Exploit, Modes_of_Introduction, Relationships
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Failure of TRNG
2009-05-27Failure to Handle Insufficient Entropy in TRNG

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Page Last Updated: March 29, 2018