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Home > CWE List > CWE-755: Improper Handling of Exceptional Conditions (4.18)
ID
CWE Glossary Definition

CWE-755: Improper Handling of Exceptional Conditions

Weakness ID: 755
Vulnerability Mapping: DISCOURAGED This CWE ID should not be used to map to real-world vulnerabilities
Abstraction: Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
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Description
The product does not handle or incorrectly handles an exceptional condition.
Common Consequences
Section HelpThis table 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.
Impact Details

Other

Scope: Other

Relationships
Section Help This table 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" (View-1000)
Nature Type ID Name
ChildOf Pillar Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things. 703 Improper Check or Handling of Exceptional Conditions
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 209 Generation of Error Message Containing Sensitive Information
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 248 Uncaught Exception
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 274 Improper Handling of Insufficient Privileges
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 280 Improper Handling of Insufficient Permissions or Privileges
ParentOf Variant Variant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. 333 Improper Handling of Insufficient Entropy in TRNG
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 390 Detection of Error Condition Without Action
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 392 Missing Report of Error Condition
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 395 Use of NullPointerException Catch to Detect NULL Pointer Dereference
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 396 Declaration of Catch for Generic Exception
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 460 Improper Cleanup on Thrown Exception
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 544 Missing Standardized Error Handling Mechanism
ParentOf Class Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource. 636 Not Failing Securely ('Failing Open')
ParentOf Base Base - a weakness that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource. 756 Missing Custom Error Page
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (View-1003)
Nature Type ID Name
MemberOf View View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries). 1003 Weaknesses for Simplified Mapping of Published Vulnerabilities
Relevant to the view "Architectural Concepts" (View-1008)
Nature Type ID Name
MemberOf Category Category - a CWE entry that contains a set of other entries that share a common characteristic. 1020 Verify Message Integrity
Modes Of Introduction
Section HelpThe different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase Note
Implementation REALIZATION: This weakness is caused during implementation of an architectural security tactic.
Applicable Platforms
Section HelpThis listing shows 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: Not Language-Specific (Undetermined Prevalence)

Likelihood Of Exploit
Medium
Demonstrative Examples

Example 1


The following example attempts to resolve a hostname.

(bad code)
Example Language: Java
protected void doPost (HttpServletRequest req, HttpServletResponse res) throws IOException {
String ip = req.getRemoteAddr();
InetAddress addr = InetAddress.getByName(ip);
...
out.println("hello " + addr.getHostName());
}

A DNS lookup failure will cause the Servlet to throw an exception.



Example 2


The following example attempts to allocate memory for a character. After the call to malloc, an if statement is used to check whether the malloc function failed.

(bad code)
Example Language: C
foo=malloc(sizeof(char)); //the next line checks to see if malloc failed
if (foo==NULL) {
//We do nothing so we just ignore the error.
}

The conditional successfully detects a NULL return value from malloc indicating a failure, however it does not do anything to handle the problem. Unhandled errors may have unexpected results and may cause the program to crash or terminate.

Instead, the if block should contain statements that either attempt to fix the problem or notify the user that an error has occurred and continue processing or perform some cleanup and gracefully terminate the program. The following example notifies the user that the malloc function did not allocate the required memory resources and returns an error code.

(good code)
Example Language: C
foo=malloc(sizeof(char)); //the next line checks to see if malloc failed
if (foo==NULL) {
printf("Malloc failed to allocate memory resources");
return -1;
}


Example 3


The following code mistakenly catches a NullPointerException.

(bad code)
Example Language: Java
try {
mysteryMethod();
} catch (NullPointerException npe) {
}


Selected Observed Examples

Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.

Reference Description
SDK for OPC Unified Architecture (OPC UA) server has uncaught exception when a socket is blocked for writing but the server tries to send an error
Chain: JavaScript-based cryptocurrency library can fall back to the insecure Math.random() function instead of reporting a failure (CWE-392), thus reducing the entropy (CWE-332) and leading to generation of non-unique cryptographic keys for Bitcoin wallets (CWE-1391)
virtual interrupt controller in a virtualization product allows crash of host by writing a certain invalid value to a register, which triggers a fatal error instead of returning an error code
Chain: OS kernel does not properly handle a failure of a function call (CWE-755), leading to an unlock of a resource that was not locked (CWE-832), with resultant crash.
Memberships
Section HelpThis 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.
Nature Type ID Name
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 880 CERT C++ Secure Coding Section 12 - Exceptions and Error Handling (ERR)
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 962 SFP Secondary Cluster: Unchecked Status Condition
MemberOf CategoryCategory - a CWE entry that contains a set of other entries that share a common characteristic. 1405 Comprehensive Categorization: Improper Check or Handling of Exceptional Conditions
Vulnerability Mapping Notes
Usage DISCOURAGED
(this CWE ID should not be used to map to real-world vulnerabilities)
Reason Abstraction

Rationale

This CWE entry is a level-1 Class (i.e., a child of a Pillar). It might have lower-level children that would be more appropriate

Comments

Examine children of this entry to see if there is a better fit
References
[REF-1374] Unciphered. "Randstorm: You Can't Patch a House of Cards". 2023年11月14日.
<https://www.unciphered.com/disclosure-of-vulnerable-bitcoin-wallet-library-2/>. (URL validated: 2025年07月29日)
Content History
Submissions
Submission Date Submitter Organization
2009年03月03日
(CWE 1.3, 2009年03月10日) 		CWE Content Team MITRE
New entry for reorganization of CWE-703.
Modifications
Modification Date Modifier Organization
2025年09月09日
(CWE 4.18, 2025年09月09日) 		CWE Content Team MITRE
updated References
2024年02月29日
(CWE 4.14, 2024年02月29日) 		CWE Content Team MITRE
updated Demonstrative_Examples, Mapping_Notes, Observed_Examples, References, Relationships
2023年06月29日 CWE Content Team MITRE
updated Mapping_Notes, Relationships
2023年04月27日 CWE Content Team MITRE
updated Relationships
2023年01月31日 CWE Content Team MITRE
updated Description, Relationships
2022年04月28日 CWE Content Team MITRE
updated Relationships
2021年10月28日 CWE Content Team MITRE
updated Observed_Examples
2020年06月25日 CWE Content Team MITRE
updated Relationships
2020年02月24日 CWE Content Team MITRE
updated Relationships
2019年06月20日 CWE Content Team MITRE
updated Relationships
2017年11月08日 CWE Content Team MITRE
updated Likelihood_of_Exploit, Modes_of_Introduction, Relationships, Taxonomy_Mappings
2017年01月19日 CWE Content Team MITRE
updated Relationships
2014年07月30日 CWE Content Team MITRE
updated Relationships
2012年05月11日 CWE Content Team MITRE
updated Relationships
2011年09月13日 CWE Content Team MITRE
updated Relationships, Taxonomy_Mappings
2011年06月01日 CWE Content Team MITRE
updated Common_Consequences
2011年03月29日 CWE Content Team MITRE
updated Relationships
2010年12月13日 CWE Content Team MITRE
updated Description, Observed_Examples
2009年12月28日 CWE Content Team MITRE
updated Applicable_Platforms, Likelihood_of_Exploit, Time_of_Introduction
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Page Last Updated: September 09, 2025

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