CVE-2003-1294 in Xscreensaver
Summary
by MITRE
Xscreensaver before 4.15 creates temporary files insecurely in (1) driver/passwd-kerberos.c, (2) driver/xscreensaver-getimage-video, (3) driver/xscreensaver.kss.in, and the (4) vidwhacker and (5) webcollage screensavers, which allows local users to overwrite arbitrary files via a symlink attack.
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Analysis
by VulDB Data Team • 06/19/2019
The vulnerability described in CVE-2003-1294 represents a critical insecure temporary file creation flaw affecting Xscreensaver versions prior to 4.15. This issue manifests across multiple components within the xscreensaver suite including driver modules and various screensaver implementations. The core problem stems from the improper handling of temporary files during the execution of security-sensitive operations, creating opportunities for privilege escalation and arbitrary file overwrite attacks. The vulnerability affects systems where xscreensaver is installed with elevated privileges, particularly when running as root or with setuid permissions.
The technical implementation of this flaw occurs in several specific locations within the xscreensaver codebase where temporary files are created without proper security measures. In the driver/passwd-kerberos.c module, the insecure temporary file creation allows attackers to manipulate authentication processes. The driver/xscreensaver-getimage-video component suffers from similar issues when processing video data, while driver/xscreensaver.kss.in contains insecure temporary file handling during key sequence processing. Additionally, the vidwhacker and webcollage screensavers demonstrate the same vulnerability pattern during their execution phases. These insecure temporary file operations typically involve creating files in world-writable directories without proper file permission checks or unique naming schemes that would prevent symlink attacks.
The operational impact of this vulnerability extends beyond simple file overwrite capabilities to encompass potential privilege escalation scenarios. Local users can exploit this flaw to overwrite arbitrary files with malicious content, potentially including system binaries, configuration files, or sensitive data. When xscreensaver executes with elevated privileges, attackers can leverage this vulnerability to compromise the entire system. The attack vector relies on symbolic link manipulation where an attacker creates a symlink in a temporary directory that will be accessed by the xscreensaver process. This creates a race condition scenario where the attacker's symlink is resolved before the legitimate temporary file creation, allowing for unauthorized file modification. The vulnerability demonstrates characteristics consistent with CWE-377: Insecure Temporary Files and CWE-378: Poor File Permissions, both of which fall under the broader category of insecure file handling practices.
The exploitation of this vulnerability aligns with several techniques documented in the MITRE ATT&CK framework, particularly those related to privilege escalation and persistence mechanisms. Attackers can utilize this flaw to establish persistent access or escalate privileges by overwriting critical system files or binaries. The vulnerability also represents a potential entry point for lateral movement within compromised systems, as the attacker can manipulate files that may be accessed by other system processes. Security professionals should note that this vulnerability has been classified as a local privilege escalation vector, making it particularly dangerous in multi-user environments where xscreensaver runs with elevated permissions. The insecure temporary file creation pattern observed here is commonly exploited in various attack scenarios and represents a fundamental security weakness that can be leveraged for broader system compromise.
Mitigation strategies for this vulnerability require immediate patching of xscreensaver installations to version 4.15 or later where the insecure temporary file handling has been corrected. System administrators should also implement proper file permission controls and ensure that temporary directories used by xscreensaver are properly secured with appropriate ownership and access restrictions. The implementation of secure temporary file creation practices, including the use of unique naming schemes and proper file permission checks, should be enforced throughout the xscreensaver codebase. Additionally, monitoring for suspicious file access patterns and implementing proper system integrity checking can help detect exploitation attempts. Organizations should also consider implementing network segmentation and privilege separation to limit the potential impact of successful exploitation, as the vulnerability's effectiveness depends on the elevated privileges with which xscreensaver operates.