Unchecked Error Condition
Weakness ID: 391 (Weakness Base)Status: Incomplete
+ Description

Description Summary

Ignoring exceptions and other error conditions may allow an attacker to induce unexpected behavior unnoticed.
+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Applicable Platforms



+ Likelihood of Exploit


+ Demonstrative Examples

Example 1

The following code excerpt ignores a rarely-thrown exception from doExchange().

(Bad Code)
Example Language: Java 
try {
catch (RareException e) {

// this can never happen

If a RareException were to ever be thrown, the program would continue to execute as though nothing unusual had occurred. The program records no evidence indicating the special situation, potentially frustrating any later attempt to explain the program's behavior.

+ Potential Mitigations

Requirements Specification: The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem.

Requirements Specification: A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added.

Phase: Implementation

Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.

+ Other Notes

Just about every serious attack on a software system begins with the violation of a programmer's assumptions. After the attack, the programmer's assumptions seem flimsy and poorly founded, but before an attack many programmers would defend their assumptions well past the end of their lunch break. Two dubious assumptions that are easy to spot in code are "this method call can never fail" and "it doesn't matter if this call fails". When a programmer ignores an exception, they implicitly state that they are operating under one of these assumptions.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfCategoryCategory388Error Handling
Seven Pernicious Kingdoms (primary)700
ChildOfCategoryCategory389Error Conditions, Return Values, Status Codes
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class703Failure to Handle Exceptional Conditions
Research Concepts (primary)1000
ChildOfCategoryCategory728OWASP Top Ten 2004 Category A7 - Improper Error Handling
Weaknesses in OWASP Top Ten (2004) (primary)711
ChildOfCategoryCategory743CERT C Secure Coding Section 09 - Input Output (FIO)
Weaknesses Addressed by the CERT C Secure Coding Standard (primary)734
ChildOfCategoryCategory746CERT C Secure Coding Section 12 - Error Handling (ERR)
Weaknesses Addressed by the CERT C Secure Coding Standard734
MemberOfViewView630Weaknesses Examined by SAMATE
Weaknesses Examined by SAMATE (primary)630
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
PLOVERUnchecked Return Value
7 Pernicious KingdomsEmpty Catch Block
CLASPUncaught exception
OWASP Top Ten 2004A7CWE More SpecificImproper Error Handling
CERT C Secure CodingERR00-CAdopt and implement a consistent and comprehensive error-handling policy
CERT C Secure CodingFIO04-CDetect and handle input and output errors
CERT C Secure CodingFIO33-CDetect and handle input output errors resulting in undefined behavior
+ White Box Definitions

A weakness where code path has:

1. start statement that changes a state of the system resource

2. end statement that accesses the system resource, where the changed and the assumed state of the system resource are not equal.

3. the state of the resource is not compatible with the type of access being performed by the end statement

+ Maintenance Notes

This entry needs significant modification. It currently combines information from three different taxonomies, but each taxonomy is talking about a slightly different issue.

+ Content History
Submission DateSubmitterOrganizationSource
PLOVERExternally Mined
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-08-01KDM AnalyticsExternal
added/updated white box definitions
Suggested OWASP Top Ten 2004 mapping
2008-09-08CWE Content TeamMITREInternal
updated Maintenance Notes, Relationships, Other Notes, Taxonomy Mappings
2008-11-24CWE Content TeamMITREInternal
updated Relationships, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Demonstrative Examples
2009-07-17KDM AnalyticsExternal
Improved the White Box Definition
2009-07-27CWE Content TeamMITREInternal
updated White Box Definitions