Insecure Temporary File

Creating and using insecure temporary files can leave application and system data vulnerable to attack.


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 uses a temporary file for storing intermediate data gathered from the network before it is processed.

if (tmpnam_r(filename)) {

  FILE* tmp = fopen(filename,"wb+");
  while((recv(sock,recvbuf,DATA_SIZE, 0) > 0)&(amt!=0)) amt = fwrite(recvbuf,1,DATA_SIZE,tmp);


This otherwise unremarkable code is vulnerable to a number of different attacks because it relies on an insecure method for creating temporary files. The vulnerabilities introduced by this function and others are described in the following sections. The most egregious security problems related to temporary file creation have occurred on Unix-based operating systems, but Windows applications have parallel risks. This section includes a discussion of temporary file creation on both Unix and Windows systems. Methods and behaviors can vary between systems, but the fundamental risks introduced by each are reasonably constant.

See Also

SEI CERT C Coding Standard - Guidelines 14. Concurrency (CON)

Weaknesses in this category are related to the rules and recommendations in the Concurrency (CON) section of the SEI CERT C Coding Standard.

SEI CERT Oracle Secure Coding Standard for Java - Guidelines 13. Input Output (FIO)

Weaknesses in this category are related to the rules and recommendations in the Input Output (FIO) section of the SEI CERT Oracle Secure Coding Standard for Java.

SFP Secondary Cluster: Exposure Temporary File

This category identifies Software Fault Patterns (SFPs) within the Exposure Temporary File cluster.

Comprehensive CWE Dictionary

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

Weaknesses without Software Fault Patterns

CWE identifiers in this view are weaknesses that do not have associated Software Fault Patterns (SFPs), as covered by the CWE-888 view. As such, they represent gaps in...

Weaknesses Introduced During Implementation

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

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