Multiple Operations on Resource in Single-Operation Context

The product performs the same operation on a resource two or more times, when the operation should only be applied once.


The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

The following code shows a simple example of a double free vulnerability.

char* ptr = (char*)malloc (SIZE);
if (abrt) {

Double free vulnerabilities have two common (and sometimes overlapping) causes:

Error conditions and other exceptional circumstances

Confusion over which part of the program is responsible for freeing the memory

Although some double free vulnerabilities are not much more complicated than this example, most are spread out across hundreds of lines of code or even different files. Programmers seem particularly susceptible to freeing global variables more than once.

Example Two

This code binds a server socket to port 21, allowing the server to listen for traffic on that port.

void bind_socket(void) {

  int server_sockfd;
  int server_len;
  struct sockaddr_in server_address;

  /*unlink the socket if already bound to avoid an error when bind() is called*/

  server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

  server_address.sin_family = AF_INET;
  server_address.sin_port = 21;
  server_address.sin_addr.s_addr = htonl(INADDR_ANY);
  server_len = sizeof(struct sockaddr_in);

  bind(server_sockfd, (struct sockaddr *) &s1, server_len);


This code may result in two servers binding a socket to same port, thus receiving each other's traffic. This could be used by an attacker to steal packets meant for another process, such as a secure FTP server.

See Also

Comprehensive Categorization: Poor Coding Practices

Weaknesses in this category are related to poor coding practices.

SFP Secondary Cluster: Life Cycle

This category identifies Software Fault Patterns (SFPs) within the Life Cycle cluster.

CERT C++ Secure Coding Section 09 - Input Output (FIO)

Weaknesses in this category are related to rules in the Input Output (FIO) section of the CERT C++ Secure Coding Standard. Since not all rules map to specific weakness...

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.

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