CVE-2020-36657 in uptimed
Summary
by MITRE • 01/26/2023
uptimed before 0.4.6-r1 on Gentoo allows local users (with access to the uptimed user account) to gain root privileges by creating a hard link within the /var/spool/uptimed directory, because there is an unsafe chown -R call.
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Analysis
by VulDB Data Team • 04/01/2025
The vulnerability CVE-2020-36657 represents a privilege escalation flaw in the uptimed service version 0.4.6-r1 and earlier on Gentoo Linux systems. This issue affects local users who already possess access to the uptimed user account, creating a significant security risk that can be exploited to gain root privileges. The vulnerability stems from improper privilege handling within the service's directory management operations, specifically involving the chown command execution.
The technical root cause of this vulnerability lies in the unsafe execution of the chown -R command within the /var/spool/uptimed directory. When a malicious user with access to the uptimed account creates a hard link to a target file within this directory, the service's improper handling of file ownership changes allows for privilege escalation. This behavior directly violates the principle of least privilege and demonstrates poor input validation and file system access control mechanisms. The vulnerability is classified as a privilege escalation issue with a CWE identifier of CWE-269, which specifically addresses improper privileges assigned to a resource.
The operational impact of this vulnerability is substantial as it enables local users to bypass normal access controls and elevate their privileges to root level. Attackers can exploit this by leveraging the hard link creation technique to manipulate file ownership and subsequently gain system-level access. This type of vulnerability falls under the ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and represents a common attack pattern where adversaries leverage existing system access to escalate their privileges. The vulnerability is particularly dangerous because it requires minimal initial access - only the ability to create files as the uptimed user account.
Mitigation strategies for this vulnerability include updating to uptimed version 0.4.6-r1 or later, which contains the necessary patches to address the unsafe chown -R call. System administrators should also implement proper file system permissions and access controls to prevent unauthorized users from creating files in sensitive directories. Additionally, the service should be configured to use more secure file handling methods that do not rely on unsafe recursive ownership changes. Regular security audits and monitoring of system privileges should be implemented to detect and prevent similar issues. The fix typically involves implementing proper file ownership validation and ensuring that recursive chown operations are performed with appropriate safeguards to prevent unauthorized privilege escalation. Organizations should also consider implementing additional security measures such as mandatory access controls and privilege separation techniques to minimize the impact of such vulnerabilities.