CVE-2011-4060 in Neutrino RTOS
Summary
by MITRE
The runtime linker in QNX Neutrino RTOS 6.5.0 does not properly clear the LD_DEBUG_OUTPUT and LD_DEBUG environment variables when a program is spawned from a setuid program, which allows local users to overwrite files via a symlink attack.
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Analysis
by VulDB Data Team • 01/26/2018
The vulnerability described in CVE-2011-4060 affects the runtime linker component of QNX Neutrino RTOS version 6.5.0, specifically addressing a critical security flaw in how environment variables are handled during program execution. This issue manifests when a setuid program spawns a new process, creating an opportunity for privilege escalation through file system manipulation. The runtime linker in question fails to properly sanitize the LD_DEBUG_OUTPUT and LD_DEBUG environment variables, which are typically used for debugging purposes but can be exploited when retained across process boundaries. The flaw directly relates to improper privilege handling and environment variable management within the operating system's execution framework, creating a persistent security weakness that can be leveraged by local attackers with minimal privileges.
The technical implementation of this vulnerability stems from the runtime linker's failure to reset or clear specific environment variables when transitioning from a setuid context to a regular user context. When a setuid program executes another program, the LD_DEBUG_OUTPUT and LD_DEBUG environment variables may retain their values from the parent process, allowing an attacker to manipulate these variables to control where debug output is written. This behavior creates a symlink attack vector where a local user can create symbolic links that point to sensitive system files, and when the vulnerable runtime linker processes these variables, it can overwrite the target files with arbitrary content. The flaw represents a classic case of insecure environment variable handling that violates fundamental security principles of privilege separation and process isolation.
The operational impact of this vulnerability extends beyond simple file overwriting, as it enables attackers to potentially compromise system integrity and confidentiality. Local users can exploit this weakness to modify critical system files, configuration data, or even system binaries that are written to by the runtime linker process. The vulnerability is particularly dangerous because it operates within the system's core execution framework, meaning that successful exploitation could lead to privilege escalation, data corruption, or complete system compromise. Attackers can leverage this flaw to overwrite files that are not directly accessible through normal user permissions, effectively bypassing traditional access controls and file system protections. This vulnerability affects systems running QNX Neutrino RTOS 6.5.0 and potentially other versions that share similar runtime linker implementations, making it a widespread concern for embedded systems and real-time applications that depend on this operating system.
Mitigation strategies for CVE-2011-4060 should focus on both immediate patching and operational security measures. The primary solution involves updating to a patched version of QNX Neutrino RTOS that properly clears environment variables during setuid transitions, which aligns with the principle of least privilege and secure coding practices. System administrators should implement environment variable sanitization procedures that ensure LD_DEBUG_OUTPUT and LD_DEBUG are explicitly cleared when transitioning between privilege levels. Additionally, organizations should conduct comprehensive security audits to identify all setuid programs that may be vulnerable to this class of attack, implementing mandatory file system permissions and monitoring for suspicious symlink creation. The vulnerability demonstrates the importance of following secure coding guidelines such as those outlined in the CWE database under categories related to environment variable handling and privilege management, and aligns with ATT&CK techniques for privilege escalation through environment manipulation and local execution. Organizations should also consider implementing file integrity monitoring solutions and regular security assessments to detect and prevent exploitation attempts targeting similar runtime linker vulnerabilities.