CWE-378: Creation of Temporary File With Insecure Permissions

Description

Opening temporary files without appropriate measures or controls can leave the file, its contents and any function that it impacts vulnerable to attack.

Abstraction: BaseA weakness specific enough to point to detection and prevention methods.
Likelihood of exploit: High
Status: Draft

Common consequences

Confidentiality
Read Application Data
If the temporary file can be read by the attacker, sensitive information may be in that file which could be revealed.
AuthorizationOther
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.
IntegrityOther
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.

Potential mitigations

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

Related weaknesses

Parent weaknesses

CWE-377Insecure Temporary File

CAPEC attack patterns that exploit it

CWE 4.20 links no CAPEC attack pattern to this weakness.

Common consequences

Confidentiality

Read Application Data

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

AuthorizationOther

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.

IntegrityOther

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.

Potential mitigations

Requirements

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

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.

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.