CVE-2008-4640 in jhead
Summary
by MITRE
The DoCommand function in jhead.c in Matthias Wandel jhead 2.84 and earlier allows local users to delete arbitrary files via vectors involving a modified input filename in which (1) a final "z" character is replaced by a "t" character or (2) a final "t" character is replaced by a "z" character.
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Analysis
by VulDB Data Team • 08/23/2019
The vulnerability described in CVE-2008-4640 represents a critical file deletion flaw within the jhead utility version 2.84 and earlier, which is widely used for processing digital camera image files. This utility, developed by Matthias Wandel, is commonly employed for extracting and manipulating metadata from jpeg images, making it a frequently used tool in digital forensics and image processing workflows. The vulnerability stems from insufficient input validation within the DoCommand function in jhead.c, creating a path traversal condition that can be exploited by local attackers to delete arbitrary files on the system where the utility is executed.
The technical implementation of this vulnerability exploits a specific string manipulation pattern that occurs during filename processing within the jhead utility. When processing input filenames, the software performs character replacement operations that inadvertently create conditions where legitimate filenames can be transformed into paths pointing to system-critical files. The flaw specifically manifests when a filename ends with either a "z" or "t" character, as the replacement logic fails to properly sanitize these inputs. This creates a scenario where an attacker can craft a malicious filename that, when processed by jhead, results in unintended file deletion operations on the target system.
The operational impact of this vulnerability extends beyond simple file deletion, as it represents a privilege escalation vector that can be leveraged by local attackers to compromise system integrity. Since jhead is often executed with elevated privileges during automated image processing workflows or system maintenance tasks, the vulnerability can be exploited to remove critical system files, configuration data, or security-related components. This type of vulnerability falls under the CWE-22 category for Path Traversal and aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as it enables arbitrary command execution through manipulated file operations. The vulnerability is particularly concerning in environments where jhead is used in automated processing pipelines, as it can be exploited without requiring network access or complex attack chains.
Mitigation strategies for this vulnerability require immediate patching of the jhead utility to version 2.85 or later, which includes proper input validation and sanitization of filename parameters. System administrators should also implement restrictive file permissions on jhead installations and consider running the utility with minimal required privileges to limit potential damage from exploitation. Additionally, input validation should be implemented at the application level to prevent modification of filenames that could lead to unintended file system operations, particularly focusing on the specific character replacement patterns that trigger the vulnerability. Organizations should conduct vulnerability assessments to identify systems running affected versions of jhead and ensure proper access controls are in place to prevent unauthorized execution of the utility with elevated privileges.