CVE-2008-4935 in aview
Summary
by MITRE
asciiview in aview 1.3.0 allows local users to overwrite arbitrary files via a symlink attack on a /tmp/aview#####.pgm temporary file.
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Analysis
by VulDB Data Team • 08/22/2019
The vulnerability identified as CVE-2008-4935 represents a classic race condition and insecure temporary file handling issue within the aview image viewer application version 1.3.0. This flaw resides in the asciiview component which processes image files and generates temporary output files in the /tmp directory. The vulnerability stems from the application's failure to properly secure temporary file creation processes, creating a window of opportunity for malicious local users to exploit the system.
The technical implementation of this vulnerability involves the creation of symbolic links that can be manipulated by attackers to redirect the application's temporary file operations. When aview processes certain image formats, it creates temporary files with predictable naming patterns such as /tmp/aview#####.pgm where the hash characters represent random numbers. Attackers can create malicious symbolic links with these predictable names before the legitimate application creates its temporary files, effectively setting up a symlink attack that allows them to overwrite arbitrary files on the system with arbitrary content. This type of vulnerability falls under the CWE-362 category of Race Conditions and is particularly dangerous because it operates at the privilege level of the user running the application.
The operational impact of this vulnerability extends beyond simple file overwrites, as it can be leveraged for privilege escalation or persistent system compromise. Local attackers with basic user privileges can exploit this weakness to modify critical system files, configuration data, or even executable programs that might be processed by the application. The vulnerability is particularly concerning because it does not require special privileges or network access, making it easily exploitable within local network environments. According to ATT&CK framework, this represents a technique for privilege escalation and persistence through file system manipulation, specifically categorized under T1059 for command and scripting interpreter and T1546 for event triggered execution.
Mitigation strategies for CVE-2008-4935 should focus on implementing proper temporary file handling procedures that prevent symbolic link attacks. The most effective approach involves using secure temporary file creation methods that check for the existence of temporary files before writing to them, or using directory-specific temporary file creation mechanisms that prevent symlink attacks. System administrators should ensure that the aview application is updated to versions that address this vulnerability, as the original version 1.3.0 contains no built-in protections against such attacks. Additionally, implementing proper file system permissions and using secure temporary directory locations with restricted write access can significantly reduce the attack surface. Organizations should also consider implementing monitoring for suspicious file creation patterns in the /tmp directory and establishing proper privilege separation between user processes and system-critical files to prevent unauthorized modifications that could lead to broader system compromise.