CVE-2012-5519 in CUPS
Summary
by MITRE
CUPS 1.4.4, when running in certain Linux distributions such as Debian GNU/Linux, stores the web interface administrator key in /var/run/cups/certs/0 using certain permissions, which allows local users in the lpadmin group to read or write arbitrary files as root by leveraging the web interface.
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Analysis
by VulDB Data Team • 12/20/2021
The vulnerability identified as CVE-2012-5519 affects the Common Unix Printing System (CUPS) version 1.4.4, specifically within certain Linux distributions including Debian GNU/Linux. This issue represents a critical privilege escalation vulnerability that stems from improper file permissions and access control mechanisms within the CUPS web interface implementation. The vulnerability occurs when the system stores the web interface administrator key in the /var/run/cups/certs/0 file with insufficiently restrictive permissions, creating a path for local users to gain elevated privileges.
The technical flaw lies in the insecure handling of cryptographic certificates and administrative keys within the CUPS printing system. When the web interface administrator key is stored in the /var/run/cups/certs/0 location with inadequate permission settings, local users who belong to the lpadmin group can exploit this weakness to read or write arbitrary files as the root user. This represents a classic privilege escalation vulnerability where a user with limited system access can leverage a misconfigured file permission to gain root-level privileges. The vulnerability is particularly concerning because it requires minimal user interaction and leverages existing group membership rather than requiring additional attack vectors.
From an operational impact perspective, this vulnerability allows local users with lpadmin group membership to achieve root-level access to the system, potentially enabling complete compromise of the affected machine. Attackers could use this privilege escalation to modify system files, install malicious software, create new user accounts, or exfiltrate sensitive data. The impact extends beyond just the printing service itself, as the compromised system could serve as a foothold for further attacks within a network environment. This vulnerability is particularly dangerous in multi-user environments where multiple users might be granted lpadmin privileges for legitimate printing administration purposes.
The vulnerability aligns with CWE-732: Incorrect Permission Assignment for Critical Resource, which specifically addresses cases where critical system resources are assigned improper permissions that allow unauthorized access. This flaw also relates to ATT&CK technique T1068: Exploitation for Privilege Escalation, where adversaries leverage system vulnerabilities to gain elevated privileges. The attack vector requires local system access and group membership, making it a low-barrier privilege escalation opportunity that could be exploited by both malicious insiders and external attackers who have gained initial access to the system. Organizations should implement proper file permission management and regularly audit system configurations to prevent such vulnerabilities from persisting in production environments.
Mitigation strategies should include immediate patching of affected CUPS versions, proper configuration of file permissions for certificate storage directories, and implementation of principle of least privilege for group memberships. System administrators should ensure that the /var/run/cups/certs/0 file and related directories have restrictive permissions that prevent unauthorized access. Regular security audits and monitoring for improper file permissions can help detect and remediate similar vulnerabilities before they can be exploited. Additionally, organizations should consider implementing additional security controls such as mandatory access controls and privilege separation mechanisms to reduce the impact of such vulnerabilities when they do occur.