CWE-378

Base Abstraction Level
Pillar — Highest-level weakness category
Class — Abstract, language-independent
Base — Specific enough to detect
Variant — Tied to specific technology
Compound — Requires multiple weaknesses Draft MITRE CWE Status
Stable — Fully reviewed and complete
Draft — Under development, may change
Incomplete — Partially defined by MITRE
Deprecated — No longer recommended
Obsolete — Replaced by another CWE Exploit: High
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.

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.

Authorization, Other — 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 — 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.

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.

Detection

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)