CVE-2005-2748 in Mac OS X
Summary
by MITRE
the malloc function in the libsystem library in apple mac os x 10.3.9 and 10.4.2 allows local users to overwrite arbitrary files by setting the malloclogfile environment variable to the target file before running a setuid application.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability described in CVE-2005-2748 represents a critical security flaw in Apple Mac OS X versions 10.3.9 and 10.4.2, specifically within the libsystem library's malloc function. This issue arises from improper handling of the malloclogfile environment variable, which creates a dangerous condition where local users can manipulate file system access through setuid applications. The vulnerability operates by leveraging the environment variable to redirect malloc logging output to arbitrary file locations, effectively enabling privilege escalation through file overwrite operations.
The technical implementation of this flaw involves the malloc function's interaction with the malloclogfile environment variable, which is typically intended for debugging purposes but becomes exploitable when set before executing setuid applications. When a setuid application is launched with this specific environment variable configured, the malloc function attempts to write log data to the specified file path, bypassing normal file access controls and permissions. This behavior creates a path traversal scenario where the logged data can overwrite existing files with the privileges of the setuid process, potentially allowing attackers to modify critical system files or replace binaries with malicious versions.
The operational impact of this vulnerability extends beyond simple file overwrites to encompass broader privilege escalation capabilities within the Mac OS X environment. Since the exploitation occurs before the setuid application executes, the attacker can leverage this to modify files that would normally require elevated privileges to change. This vulnerability particularly affects system integrity by allowing local users to potentially replace critical system binaries or configuration files, which could lead to persistent backdoors or complete system compromise. The flaw demonstrates a fundamental issue in how environment variables are processed within system libraries, creating an attack surface that bypasses standard Unix permission models.
Security mitigations for this vulnerability should focus on implementing proper environment variable sanitization within system libraries and restricting the ability to set critical debugging variables before setuid execution. The recommended approach involves modifying the malloc function behavior to ignore or validate the malloclogfile environment variable when running with elevated privileges, ensuring that logging operations cannot be used to overwrite arbitrary files. Additionally, system administrators should implement strict file permission controls and monitor for unusual file modification patterns, particularly around setuid binaries. This vulnerability aligns with CWE-276, which addresses improper file permissions, and represents a classic example of environment variable manipulation leading to privilege escalation. The attack pattern corresponds to techniques found in the ATT&CK framework under privilege escalation tactics, specifically focusing on environment variable manipulation and setuid binary exploitation. Organizations should also consider implementing mandatory access controls and runtime application whitelisting to prevent unauthorized modification of system files even if such vulnerabilities are present in older system versions.