CVE-2005-3346 in OSH
Summary
by MITRE
Buffer overflow in the environment variable substitution code in main.c in OSH 1.7-14 allows local users to inject arbitrary environment variables, such as LD_PRELOAD, via pathname arguments of the form "$VAR/EVAR=arg", which cause the EVAR portion to be appended to a buffer returned by a getenv function call.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability described in CVE-2005-3346 represents a critical buffer overflow condition within the OpenSH (OSH) shell version 1.7-14 that stems from improper handling of environment variable substitution during pathname argument processing. This flaw exists in the main.c source file where the shell processes command line arguments containing environment variable references. The specific implementation issue occurs when the shell encounters pathname arguments formatted as "$VAR/EVAR=arg" where it incorrectly handles the EVAR portion of the argument. The buffer overflow vulnerability arises because the shell does not properly validate or constrain the length of the EVAR component before appending it to a buffer that is subsequently processed by getenv function calls, creating a potential exploitation vector for privilege escalation attacks.
The technical exploitation of this vulnerability relies on the shell's insufficient input validation during environment variable substitution operations. When processing arguments containing the "$VAR/EVAR=arg" pattern, the shell's parsing logic fails to properly bound-check the EVAR portion before concatenating it to an internal buffer. This buffer, which is typically returned by a getenv function call, becomes vulnerable to overflow when the EVAR component exceeds the allocated buffer size. The vulnerability specifically enables attackers to inject arbitrary environment variables, particularly LD_PRELOAD, which can be leveraged to load malicious shared libraries and execute code with the privileges of the shell process. This represents a classic buffer overflow scenario that aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which addresses stack-based buffer overflow vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and denial of service conditions. Local users who can execute commands through the vulnerable OSH shell can exploit this flaw to inject malicious environment variables that modify the runtime behavior of the shell and potentially other processes. The LD_PRELOAD injection capability is particularly dangerous as it allows attackers to preload malicious libraries that can intercept and modify system calls, effectively providing a mechanism for code injection and privilege escalation. The vulnerability demonstrates poor input validation practices and inadequate buffer management that violates fundamental security principles for shell implementations. Attackers can leverage this weakness to bypass security controls, escalate privileges, and potentially gain unauthorized access to system resources, making it a significant concern for systems where local users have access to shell environments.
Mitigation strategies for this vulnerability require immediate patching of the OSH shell to address the buffer overflow condition in the environment variable substitution code. System administrators should ensure that all instances of OSH version 1.7-14 are updated to patched versions that properly validate buffer boundaries during environment variable processing. Additionally, implementing proper input sanitization measures and bounds checking in shell argument parsing can prevent similar vulnerabilities from occurring. The use of privilege separation techniques and mandatory access controls can limit the potential damage from successful exploitation attempts. Organizations should also consider implementing runtime protection mechanisms such as stack canaries, address space layout randomization, and non-executable stack protections to make exploitation more difficult. From an operational security perspective, monitoring for unusual environment variable modifications and implementing least privilege principles can help detect and prevent unauthorized exploitation attempts. The vulnerability underscores the importance of secure coding practices and proper input validation in system-level software components, particularly those handling user-provided data in shell environments.