CWE-62: UNIX Hard Link

MITRE CWE weakness

Description

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

Failure for a system to check for hard links can result in vulnerability to different types of attacks. For example, an attacker can escalate their privileges if a file used by a privileged program is replaced with a hard link to a sensitive file (e.g. /etc/passwd). When the process opens the file, the attacker can assume the privileges of that process.

Common consequences

• Confidentiality, Integrity: Read Files or Directories, Modify Files or Directories

Mitigations

Architecture and Design — Follow 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.

References

• CWE page: https://cwe.mitre.org/data/definitions/62.html
• CWE list: https://cwe.mitre.org/data/index.html