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Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

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ID

CWE-365: Race Condition in Switch

Weakness ID: 365
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
The code contains a switch statement in which the switched variable can be modified while the switch is still executing, resulting in unexpected behavior.
+ Extended Description
This issue is particularly important in the case of switch statements that involve fall-through style case statements - ie., those which do not end with break. If the variable being tested by the switch changes in the course of execution, this could change the intended logic of the switch so much that it places the process in a contradictory state and in some cases could even result in memory corruption.
+ 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)
+ Relevant to the view "Development Concepts" (CWE-699)
+ 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
Implementation
+ 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

C: (Undetermined Prevalence)

C++: (Undetermined Prevalence)

Java: (Undetermined Prevalence)

C#: (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
Integrity
Other

Technical Impact: Alter Execution Logic; Unexpected State

This weakness may lead to unexpected system state, resulting in unpredictable behavior.
+ Likelihood Of Exploit
Medium
+ Demonstrative Examples

Example 1

This example has a switch statement that executes different code depending on the current time.

(bad)
Example Language:
#include <sys/types.h>
#include <sys/stat.h>
int main(argc,argv){
struct stat *sb;
time_t timer;
lstat("bar.sh",sb);
printf("%d\n",sb->st_ctime);
switch(sb->st_ctime % 2){
case 0: printf("One option\n");
break;
case 1: printf("another option\n");
break;
default: printf("huh\n");
break;

}
return 0;

}

It seems that the default case of the switch statement should never be reached, as st_ctime % 2 should always be 0 or 1. However, if st_ctime % 2 is 1 when the first case is evaluated, the time may change and st_ctime % 2 may be equal to 0 when the second case is evaluated. The result is that neither case 1 or case 2 execute, and the default option is chosen.

+ Potential Mitigations

Phase: Implementation

Variables that may be subject to race conditions should be locked before the switch statement starts and only unlocked after the statement ends.
+ 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.
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPRace condition in switch
CERT C Secure CodingPOS35-CAvoid race conditions while checking for the existence of a symbolic link
Software Fault PatternsSFP19Missing Lock
+ References
[REF-44] Michael Howard, David LeBlanc and John Viega. "24 Deadly Sins of Software Security". "Sin 13: Race Conditions." Page 205. McGraw-Hill. 2010.
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
CLASP
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Applicable_Platforms, Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2008-11-24CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2010-09-27CWE Content TeamMITRE
updated Relationships
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2011-06-27CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Demonstrative_Examples, References, Relationships
2014-06-23CWE Content TeamMITRE
updated Common_Consequences, Description, Other_Notes, Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships, Taxonomy_Mappings
2017-11-08CWE Content TeamMITRE
updated Demonstrative_Examples

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Page Last Updated: November 14, 2017