CWE

Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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ID

CWE-378: Creation of Temporary File With Insecure Permissions

Weakness ID: 378
Abstraction: Base
Structure: Simple
Status: Draft
Presentation Filter:
+ Description
Opening temporary files without appropriate measures or controls can leave the file, its contents and any function that it impacts vulnerable to attack.
+ Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

+ Relevant to the view "Research Concepts" (CWE-1000)
NatureTypeIDName
ChildOfBaseBase377Insecure Temporary File
+ Relevant to the view "Development Concepts" (CWE-699)
NatureTypeIDName
MemberOfCategoryCategory376Temporary File Issues
+ Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

PhaseNote
Architecture and Design
Implementation
+ Applicable Platforms
The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

(Language-Independent classes): (Undetermined Prevalence)

+ Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality

Technical Impact: Read Application Data

If the temporary file can be read by the attacker, sensitive information may be in that file which could be revealed.
Authorization
Other

Technical Impact: Other

If that file can be written to by the attacker, the file might be moved into a place to which the attacker does not have access. This will allow the attacker to gain selective resource access-control privileges.
Integrity
Other

Technical Impact: Other

Depending on the data stored in the temporary file, there is the potential for an attacker to gain an additional input vector which is trusted as non-malicious. It may be possible to make arbitrary changes to data structures, user information, or even process ownership.
+ Likelihood Of Exploit
High
+ Demonstrative Examples

Example 1

In the following code examples a temporary file is created and written to and after using the temporary file the file is closed and deleted from the file system.

(bad)
Example Language:
FILE *stream;
if( (stream = tmpfile()) == NULL ) {

perror("Could not open new temporary file\n");
return (-1);

}
// write data to tmp file

...
// remove tmp file
rmtmp();

However, within this C/C++ code the method tmpfile() is used to create and open the temp file. The tmpfile() method works the same way as the fopen() method would with read/write permission, allowing attackers to read potentially sensitive information contained in the temp file or modify the contents of the file.

(bad)
Example Language: Java 
try {
File temp = File.createTempFile("pattern", ".suffix");
temp.deleteOnExit();
BufferedWriter out = new BufferedWriter(new FileWriter(temp));
out.write("aString");
out.close();

}
catch (IOException e) {
}

Similarly, the createTempFile() method used in the Java code creates a temp file that may be readable and writable to all users.

Additionally both methods used above place the file into a default directory. On UNIX systems the default directory is usually "/tmp" or "/var/tmp" and on Windows systems the default directory is usually "C:\\Windows\\Temp", which may be easily accessible to attackers, possibly enabling them to read and modify the contents of the temp file.

+ Potential Mitigations

Phase: Requirements

Many contemporary languages have functions which properly handle this condition. Older C temp file functions are especially susceptible.

Phase: Implementation

Ensure that you use proper file permissions. This can be achieved by using a safe temp file function. Temporary files should be writable and readable only by the process that owns the file.

Phase: Implementation

Randomize temporary file names. This can also be achieved by using a safe temp-file function. This will ensure that temporary files will not be created in predictable places.
+ Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
NatureTypeIDName
MemberOfCategoryCategory964SFP Secondary Cluster: Exposure Temporary File
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
CLASPImproper temp file opening
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
CLASP
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigital
updated Time_of_Introduction
2008-09-08CWE Content TeamMITRE
updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings
2009-10-29CWE Content TeamMITRE
updated Common_Consequences, Other_Notes
2011-06-01CWE Content TeamMITRE
updated Common_Consequences
2012-05-11CWE Content TeamMITRE
updated Relationships
2012-10-30CWE Content TeamMITRE
updated Demonstrative_Examples, Potential_Mitigations
2014-06-23CWE Content TeamMITRE
updated Potential_Mitigations
2014-07-30CWE Content TeamMITRE
updated Relationships
2017-11-08CWE Content TeamMITRE
updated Applicable_Platforms, Demonstrative_Examples
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Improper Temporary File Opening

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Page Last Updated: November 14, 2017