CVE-2017-18018 : Security Advisory and Response

In versions of GNU Coreutils up to 8.29, a vulnerability exists in the chown and chgrp programs that allows unauthorized local users to change the ownership of any files by exploiting a timing issue.

Understanding CVE-2017-18018

This CVE identifies a security flaw in GNU Coreutils that could be leveraged by local users to modify file ownership.

What is CVE-2017-18018?

This vulnerability in GNU Coreutils up to version 8.29 allows the substitution of a regular file with a symbolic link when executing specific POSIX options, enabling unauthorized users to change file ownership.

The Impact of CVE-2017-18018

The vulnerability poses a risk of unauthorized ownership changes to sensitive files, potentially leading to data manipulation or destruction by malicious actors.

Technical Details of CVE-2017-18018

This section delves into the technical aspects of the CVE.

Vulnerability Description

The flaw in chown and chgrp programs in GNU Coreutils up to version 8.29 allows local users to replace plain files with symlinks using specific POSIX options, leading to unauthorized ownership modifications.

Affected Systems and Versions

Product: GNU Coreutils
Vendor: GNU
Versions affected: Up to 8.29

Exploitation Mechanism

The vulnerability arises due to the lack of safeguards in the chown and chgrp programs, enabling the manipulation of file ownership through a race condition.

Mitigation and Prevention

Protecting systems from CVE-2017-18018 involves taking immediate and long-term security measures.

Immediate Steps to Take

Update GNU Coreutils to version 8.30 or newer to mitigate the vulnerability.
Monitor file ownership changes for suspicious activities.

Long-Term Security Practices

Implement the principle of least privilege to restrict user capabilities.
Regularly audit and review file ownership and permissions.

Patching and Updates

Apply patches and updates provided by GNU to address the vulnerability and enhance system security.