Base · Medium

CWE-240: Improper Handling of Inconsistent Structural Elements

The product does not handle or incorrectly handles when two or more structural elements should be consistent, but are not.

CWE-240 · Base Level ·2 CVEs

Description

The product does not handle or incorrectly handles when two or more structural elements should be consistent, but are not.

Potential Impact

Integrity, Other

Varies by Context, Unexpected State

Demonstrative Examples

In the following C/C++ example the method processMessageFromSocket() will get a message from a socket, placed into a buffer, and will parse the contents of the buffer into a structure that contains the message length and the message body. A for loop is used to copy the message body into a local character string which will be passed to another method for processing.
Bad
int processMessageFromSocket(int socket) {
                        int success;
                           char buffer[BUFFER_SIZE];char message[MESSAGE_SIZE];
                           
                           // get message from socket and store into buffer
                           
                           
                           //Ignoring possibliity that buffer > BUFFER_SIZE
                           if (getMessage(socket, buffer, BUFFER_SIZE) > 0) {
                              
                                 
                                 // place contents of the buffer into message structure
                                 ExMessage *msg = recastBuffer(buffer);
                                 
                                 // copy message body into string for processing
                                 int index;for (index = 0; index < msg->msgLength; index++) {message[index] = msg->msgBody[index];}message[index] = '\0';
                                 
                                 // process message
                                 success = processMessage(message);
                           }return success;
                     }
However, the message length variable (msgLength) from the structure is used as the condition for ending the for loop without validating that msgLength accurately reflects the actual length of the message body (CWE-606). If msgLength indicates a length that is longer than the size of a message body (CWE-130), then this can result in a buffer over-read by reading past the end of the buffer (CWE-126).

Real-World CVE Examples

CVE IDDescription
CVE-2014-0160Chain: "Heartbleed" bug receives an inconsistent length parameter (CWE-130) enabling an out-of-bounds read (CWE-126), returning memory that could include private cryptographic keys and other sensitive
CVE-2009-2299Web application firewall consumes excessive memory when an HTTP request contains a large Content-Length value but no POST data.

Taxonomy Mappings

  • PLOVER: — Inconsistent Elements

Frequently Asked Questions

What is CWE-240?

CWE-240 (Improper Handling of Inconsistent Structural Elements) is a software weakness identified by MITRE's Common Weakness Enumeration. It is classified as a Base-level weakness. The product does not handle or incorrectly handles when two or more structural elements should be consistent, but are not.

How can CWE-240 be exploited?

Attackers can exploit CWE-240 (Improper Handling of Inconsistent Structural Elements) to varies by context, unexpected state. This weakness is typically introduced during the Implementation phase of software development.

How do I prevent CWE-240?

Follow secure coding practices, conduct code reviews, and use automated security testing tools (SAST/DAST) to detect this weakness early in the development lifecycle.

What is the severity of CWE-240?

CWE-240 is classified as a Base-level weakness (Medium abstraction). It has been observed in 2 real-world CVEs.