Official definition

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.

A product that allows UNIX symbolic links (symlink) as part of paths whether in internal code or through user input can allow an attacker to spoof the symbolic link and traverse the file system to unintended locations or access arbitrary files. The symbolic link can permit an attacker to read/write/corrupt a file that they originally did not have permissions to access.

Characteristics

Alternate terms

Symlink following
symlink vulnerability

Modes of introduction

Implementation: These are typically reported for temporary files or privileged programs.

Common consequences

Impact	Scope	Explanation
Read Files or Directories, Modify Files or Directories	Confidentiality, Integrity	—

Risk mitigations

ImplementationSymbolic link attacks often occur when a program creates a tmp directory that stores files/links. Access to the directory should be restricted to the program as to prevent attackers from manipulating the files.
Separation of Privilege · Architecture and DesignFollow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Detection methods

Method	Approach	Effectiveness
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.)	—

Representative vulnerabilities

Below are representative vulnerabilities related to this CWE, prioritized by severity.

Sources (4)

CWE-61: UNIX Symbolic Link (Symlink) Following

What is CWE-61?

Data statistics

Vulnerabilities mapped to CWE-61

Vulnerabilities in CISA KEV for CWE-61