CWE-478: Missing Default Case in Multiple Condition Expression
The code does not have a default case in an expression with multiple conditions, such as a switch statement.
How it's found
Missing Default Case in Multiple Condition Expression is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
If a multiple-condition expression (such as a switch in C) omits the default case but does not consider or handle all possible values that could occur, then this might lead to complex logical errors and resultant weaknesses. Because of this, further decisions are made based on poor information, and cascading failure results. This cascading failure may result in any number of security issues, and constitutes a significant failure in the system.
Vulnerable vs. safe
//Break never reached because of exit()printf("Security check failed!\n");exit(-1);break;
printf("Security check passed.\n");break;
case FAILED:case PASSED:// program execution continues...#define FAILED 0#define PASSED 1int result;...result = security_check(data);switch (result) {}...//Break never reached because of exit()printf("Security check failed!\n");exit(-1);break;
printf("Security check passed.\n");break;
printf("Unknown error (%d), exiting...\n",result);exit(-1);
case FAILED:case PASSED:default:#define FAILED 0#define PASSED 1int result;...result = security_check(data);switch (result) {}Consequences
- Varies by Context, Alter Execution Logic: Depending on the logical circumstances involved, any consequences may result: e.g., issues of confidentiality, authentication, authorization, availability, integrity, accountability, or non-repudiation.
Mitigations
- Implementation: Ensure that there are no cases unaccounted for when adjusting program flow or values based on the value of a given variable. In the case of switch style statements, the very simple act of creating a default case can, if done correctly, mitigate this situation. Often however, the default case is used simply to represent an assumed option, as opposed to working as a check for invalid input. This is poor practice and in some cases is as bad as omitting a default case entirely.
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is CWE-478?
The code does not have a default case in an expression with multiple conditions, such as a switch statement.
How do you find Missing Default Case in Multiple Condition Expression?
Missing Default Case in Multiple Condition Expression is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.
What is the impact of CWE-478?
Varies by Context, Alter Execution Logic: Depending on the logical circumstances involved, any consequences may result: e.g., issues of confidentiality, authentication, authorization, availability, integrity, accountability, or non-repudiation.
Does TurboPentest test for Missing Default Case in Multiple Condition Expression?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related CWEs
Written and reviewed by
Michel Chamberland - Founder & CEO, IntegSec
CISSP, OSCP, OSCE, CEH, GIAC, CCSK · 20+ years in offensive security
Michel has spent 20+ years on offensive security teams including IBM X-Force Red and Trustwave SpiderLabs, leading penetration tests, red team engagements, and breach response for Fortune 500 customers. He is the founder of IntegSec and the architect of TurboPentest.
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