CVE-2008-4955 in freevo
Summary
by MITRE
freevo.real in freevo 1.8.1 allows local users to overwrite arbitrary files via a symlink attack on (1) /tmp/*-#####.pid, (2) /tmp/freevo-gdb, (3) /tmp/freevo-gdb.sh, and (4) /tmp/*.stats temporary files. NOTE: this issue is only a vulnerability when a verbose debug mode is activated by modifying source code.
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Analysis
by VulDB Data Team • 10/13/2018
The vulnerability identified as CVE-2008-4955 affects the freevo media center software version 1.8.1 and represents a classic symlink attack scenario that enables local privilege escalation through file overwrite operations. This weakness resides in the application's handling of temporary files during debug mode execution, specifically targeting four critical temporary file locations including pid files, gdb debugging files, and statistics files within the /tmp directory. The vulnerability demonstrates a fundamental flaw in the software's security design where temporary file creation lacks proper validation mechanisms to prevent symbolic link attacks.
The technical implementation of this vulnerability stems from the application's failure to properly secure temporary file creation processes. When freevo operates in verbose debug mode, it creates temporary files in the /tmp directory without implementing proper file access controls or validation checks. Attackers can exploit this by creating symbolic links with the same names as the temporary files that freevo intends to create, effectively redirecting the application's write operations to arbitrary locations on the filesystem. This type of attack falls under the CWE-377 vulnerability category, specifically CWE-377: Insecure Temporary File, which is classified as a weakness in software design that allows attackers to manipulate temporary files through various means including symbolic links, hard links, or race conditions.
The operational impact of this vulnerability is significant within environments where the affected software is deployed with debug mode enabled. While the vulnerability requires manual modification of source code to activate verbose debug mode, this condition is not particularly difficult to achieve, especially in development or testing environments where debugging capabilities are frequently utilized. The potential for privilege escalation exists because the temporary files created by freevo may be owned by processes running with elevated privileges, allowing attackers to overwrite files with malicious content that could execute with higher privileges. This scenario aligns with ATT&CK technique T1059.001 for command and scripting interpreter, where attackers could leverage the overwritten files to execute malicious payloads.
The attack vector specifically targets the /tmp directory which is commonly used for temporary file storage and often has permissive permissions that allow local users to create symbolic links. The four targeted locations include patterned pid files with numeric suffixes, gdb debugging files, shell script files, and statistics files, all of which represent potential entry points for attackers to gain unauthorized access or modify system components. The vulnerability is particularly concerning because it operates under the assumption that the application will be running with sufficient privileges to write to these temporary locations, making it a potential vector for privilege escalation attacks. Organizations should note that while the vulnerability requires specific conditions to be exploited, the low complexity of the attack makes it a significant concern for systems where the affected software is deployed with debug capabilities enabled.
Mitigation strategies should focus on implementing proper temporary file creation practices that prevent symbolic link attacks through the use of secure file creation functions, proper file ownership controls, and restricting write access to temporary directories. The most effective approach involves modifying the application to use secure temporary file creation methods that either check for existing symbolic links or create files with unique, unpredictable names that cannot be pre-created by attackers. Additionally, system administrators should disable verbose debug mode in production environments and implement proper access controls to limit local user privileges that could be leveraged to create malicious symbolic links. The solution should also include monitoring for suspicious file creation patterns and implementing proper file integrity checks to detect unauthorized modifications to critical system files.