CVE-2008-4639 in jhead
Summary
by MITRE
jhead.c in Matthias Wandel jhead 2.84 and earlier allows local users to overwrite arbitrary files via a symlink attack on a temporary file.
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Analysis
by VulDB Data Team • 08/23/2019
The vulnerability identified as CVE-2008-4639 resides within the jhead utility version 2.84 and earlier, a widely used command-line tool for extracting and modifying jpeg header information. This flaw represents a classic symlink attack vulnerability that exploits insecure temporary file handling practices within the software's file processing workflow. The vulnerability specifically affects the jhead.c source file which governs the utility's core functionality for manipulating jpeg metadata.
The technical implementation of this vulnerability stems from improper handling of temporary files during the jpeg processing operation. When jhead processes a jpeg file, it creates temporary files in a predictable location without sufficient security checks to verify that these temporary files are not symbolic links. An attacker can exploit this by creating a symbolic link with a predetermined name in the directory where jhead expects to create its temporary files, thereby redirecting the utility's write operations to overwrite arbitrary files on the system. This insecure temporary file creation pattern directly violates established security principles and constitutes a privilege escalation vulnerability.
The operational impact of this vulnerability extends beyond simple file overwrites, as it provides local attackers with a mechanism to potentially modify critical system files, configuration data, or user documents. The attack requires local system access and knowledge of the target directory structure, but once executed successfully, it can lead to persistent modifications that may compromise system integrity and confidentiality. The vulnerability affects any system where jhead is installed and executed with sufficient privileges to create symbolic links, making it particularly concerning in multi-user environments or systems where users might have limited access to temporary directories.
This vulnerability aligns with CWE-354, which specifically addresses "Improper Validation of Integrity Check Values," and demonstrates poor adherence to secure coding practices as outlined in the CWE taxonomy. The attack vector maps to ATT&CK technique T1059.007 for command and script interpreter usage, though the actual exploitation occurs through file system manipulation rather than direct command execution. The vulnerability also reflects broader security concerns related to temporary file handling as referenced in various secure coding guidelines, including those from the Open Web Application Security Project. Mitigation strategies include updating to jhead version 2.85 or later, implementing proper temporary file creation with secure permissions, and using atomic file operations that prevent symlink attacks. System administrators should also consider implementing file system protections such as restrictive permissions on temporary directories and monitoring for suspicious symbolic link creation activities.