CVE-2020-14367

A flaw was found in chrony versions before 3.5.1 when creating the PID file under the /var/run/chrony folder. The file is created during chronyd startup while still running as the root user, and when its opened for writing, chronyd does not check for an existing symbolic link with the same file name. This flaw allows an attacker with privileged access to create a symlink with the default PID file name pointing to any destination file in the system, resulting in data loss and a denial of service due to the path traversal.

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://bugzilla.redhat.com/show_bug.cgi?id=1870298
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6WKABKNLCSC3MACCWU6OM2YGWVWFWFMU/
• https://security.gentoo.org/glsa/202008-23
• https://usn.ubuntu.com/4475-1/