The software reads from a buffer using buffer access mechanisms such as indexes or pointers that reference memory locations after the targeted buffer.
Extended Description
This typically occurs when the pointer or its index is incremented to a position beyond the bounds of the buffer or when pointer arithmetic results in a position outside of the valid memory location to name a few. This may result in exposure of sensitive information or possibly a crash.
Time of Introduction
Implementation
Applicable Platforms
Languages
C
C++
Common Consequences
Scope
Effect
Confidentiality
Technical Impact: Read memory
Demonstrative Examples
Example 1
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 Code)
Example Languages: C and C++
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 from the structure is used as the condition for ending the for loop without validating that the message length variable accurately reflects the length of message body. This can result in a buffer over read by reading from memory beyond the bounds of the buffer if the message length variable indicates a length that is longer than the size of a message body (CWE-130).
Chain: "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 data.
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Description
