CVE-2007-3103 in Red Hat
Summary
by MITRE
The init.d script for the X.Org X11 xfs font server on various Linux distributions might allow local users to change the permissions of arbitrary files via a symlink attack on the /tmp/.font-unix temporary file.
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Analysis
by VulDB Data Team • 06/08/2025
The vulnerability identified as CVE-2007-3103 represents a critical privilege escalation flaw within the X.Org X11 xfs font server initialization process on Linux systems. This issue manifests through the init.d script that manages the xfs font server service, creating a pathway for local attackers to manipulate file permissions through a carefully crafted symlink attack. The vulnerability specifically targets the /tmp/.font-unix temporary file location, which serves as a critical communication endpoint for the font server and is susceptible to race conditions during service initialization. The flaw enables malicious users to escalate their privileges by manipulating the temporary file permissions, potentially allowing them to modify or access files they would not normally have authorization to change.
The technical implementation of this vulnerability stems from improper handling of temporary file creation within the init.d script execution context. When the xfs font server service initializes, it creates the /tmp/.font-unix file without adequate security measures to prevent symlink attacks. This design flaw allows a local attacker to establish a symbolic link at the target location before the legitimate service process creates the file, effectively hijacking the file creation process. The vulnerability directly maps to CWE-377, which addresses insecure temporary file handling, and CWE-276, which covers improper file permissions. The attack vector specifically leverages the principle of least privilege violation, where the service process operates with elevated privileges during initialization while failing to properly validate the security context of temporary file creation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. Local attackers who successfully exploit this flaw can manipulate the font server's operational environment to gain unauthorized access to system resources, potentially leading to full system compromise. The vulnerability affects multiple Linux distributions and persists across various versions of the X.Org X11 implementation, making it particularly dangerous in enterprise environments where multiple systems may be vulnerable. The attack requires local access but does not need network connectivity, making it difficult to detect through traditional network monitoring systems and increasing the risk of insider threats or compromised accounts. This vulnerability also aligns with ATT&CK technique T1068, which covers local privilege escalation through the exploitation of system vulnerabilities, and T1548.001, covering abuse of system privileges through local account access.
Mitigation strategies for CVE-2007-3103 require immediate implementation of proper temporary file handling procedures within the init.d script. System administrators should modify the xfs font server initialization process to ensure that temporary files are created with appropriate permissions and ownership, specifically avoiding the use of predictable temporary file locations without proper atomic creation mechanisms. The recommended approach involves implementing secure file creation patterns that utilize the O_CREAT and O_EXCL flags to prevent race conditions, or alternatively, creating temporary files in directories with restricted permissions such as /var/tmp instead of /tmp. Additionally, implementing proper file permission validation during service startup and ensuring that the xfs font server runs with minimal required privileges can significantly reduce the attack surface. System hardening measures should include regular security audits of init.d scripts and service initialization processes, particularly for font servers and other X11 components, to identify and remediate similar vulnerabilities. The most effective long-term solution involves upgrading to modern X.Org implementations that properly address these security concerns and implementing comprehensive monitoring to detect unauthorized file permission changes.