CVE-2017-18188

OpenRC opentmpfiles through 0.1.3, when the fs.protected_hardlinks sysctl is turned off, allows local users to obtain ownership of arbitrary files by creating a hard link inside a directory on which chown -R will be run.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• 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.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• https://github.com/OpenRC/opentmpfiles/issues/3
• https://github.com/OpenRC/opentmpfiles/issues/3