The product reads or writes to a buffer using an index or pointer that references a memory location after the end of the buffer.
View on MITREThis typically occurs when a pointer or its index is incremented to a position after the buffer; or when pointer arithmetic results in a position after the buffer.
For an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffer's position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.
Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow. If the attacker can overwrite a pointer's worth of memory (usually 32 or 64 bits), they can redirect a function pointer to their own malicious code. Even when the attacker can only modify a single byte arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data -- such as a flag indicating whether the user is an administrator.
No mitigation information available for this CWE.
No detection method information available for this CWE.
This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.
This function allocates a buffer of 64 bytes to store the hostname, however there is no guarantee that the hostname will not be larger than 64 bytes. If an attacker specifies an address which resolves to a very large hostname, then the function may overwrite sensitive data or even relinquish control flow to the attacker.
void host_lookup(char *user_supplied_addr){ struct hostent *hp;in_addr_t *addr;char hostname[64];in_addr_t inet_addr(const char *cp); /*routine that ensures user_supplied_addr is in the right format for conversion */ validate_addr_form(user_supplied_addr);addr = inet_addr(user_supplied_addr);hp = gethostbyaddr( addr, sizeof(struct in_addr), AF_INET);strcpy(hostname, hp->h_name); }In the following example, it is possible to request that memcpy move a much larger segment of memory than assumed:
If returnChunkSize() happens to encounter an error it will return -1. Notice that the return value is not checked before the memcpy operation (CWE-252), so -1 can be passed as the size argument to memcpy() (CWE-805). Because memcpy() assumes that the value is unsigned, it will be interpreted as MAXINT-1 (CWE-195), and therefore will copy far more memory than is likely available to the destination buffer (CWE-787, CWE-788).
int returnChunkSize(void *) { /* if chunk info is valid, return the size of usable memory, * else, return -1 to indicate an error */ ... }int main() {...memcpy(destBuf, srcBuf, (returnChunkSize(destBuf)-1));...}This example applies an encoding procedure to an input string and stores it into a buffer.
The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.
char * copy_input(char *user_supplied_string){ int i, dst_index;char *dst_buf = (char*)malloc(4*sizeof(char) * MAX_SIZE);if ( MAX_SIZE <= strlen(user_supplied_string) ){die("user string too long, die evil hacker!");}dst_index = 0;for ( i = 0; i < strlen(user_supplied_string); i++ ){ if( '&' == user_supplied_string[i] ){dst_buf[dst_index++] = '&';dst_buf[dst_index++] = 'a';dst_buf[dst_index++] = 'm';dst_buf[dst_index++] = 'p';dst_buf[dst_index++] = ';';}else if ('<' == user_supplied_string[i] ){ /* encode to < */ }else dst_buf[dst_index++] = user_supplied_string[i]; }return dst_buf; }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.
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).
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; }Classic stack-based buffer overflow in media player using a long entry in a playlist
View DetailsHeap-based buffer overflow in media player using a long entry in a playlist
View DetailsOS kernel trusts userland-supplied length value, allowing reading of sensitive information
View DetailsChain: integer signedness error (CWE-195) passes signed comparison, leading to heap overflow (CWE-122)
View DetailsCWE-788: Access of Memory Location After End of Buffer is a Common Weakness Enumeration (CWE) entry maintained by MITRE. The product reads or writes to a buffer using an index or pointer that references a memory location after the end of the buffer. This typically occurs when a pointer or its index is incremented to a position after the buffer; or when pointer arithmetic results in a position after the buffer.
If exploited, CWE-788 (Access of Memory Location After End of Buffer) it can compromise Confidentiality, Integrity and Availability, leading to outcomes such as Read Memory, Modify Memory, DoS: Crash, Exit, or Restart and Execute Unauthorized Code or Commands.
CWE-788 commonly affects C, C++ and Memory-Unsafe. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
MITRE documents real CVEs mapped to CWE-788, including CVE-2009-2550, CVE-2009-2403, CVE-2009-0689, CVE-2009-0558 and CVE-2008-4113. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
A CWE (Common Weakness Enumeration) like CWE-788 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.