CVE-2010-4708 in Linux-PAM
Summary
by MITRE
The pam_env module in Linux-PAM (aka pam) 1.1.2 and earlier reads the .pam_environment file in a user s home directory, which might allow local users to run programs with an unintended environment by executing a program that relies on the pam_env PAM check.
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Analysis
by VulDB Data Team • 10/13/2021
The vulnerability described in CVE-2010-4708 resides within the pam_env module of Linux-PAM version 1.1.2 and earlier, presenting a significant security risk that can be exploited by local attackers to manipulate program execution environments. This flaw specifically targets the handling of environment variables through the .pam_environment file located in user home directories, creating a potential vector for privilege escalation and unauthorized code execution.
The technical implementation of this vulnerability stems from improper access control mechanisms within the pam_env module. When a user authenticates through PAM, the system reads the .pam_environment file from the user's home directory to establish environment variables for the session. However, the module fails to properly validate or sanitize the contents of this file, allowing malicious users to craft environment variable definitions that could be interpreted by programs relying on pam_env checks. This represents a classic case of insecure file processing and environment variable manipulation that violates the principle of least privilege and proper access control.
The operational impact of this vulnerability extends beyond simple environment manipulation, as it can enable local users to execute programs with unintended environmental contexts that may bypass security controls or exploit other weaknesses in applications. Attackers could potentially use this to inject malicious environment variables that alter program behavior, access restricted resources, or interfere with security mechanisms. The vulnerability particularly affects systems where applications depend on specific environment variable values for security decisions, making it a serious concern for enterprise environments where multiple users share systems.
This vulnerability aligns with CWE-276, which addresses improper privileges, and represents a privilege escalation vector through environment manipulation. The attack pattern follows the TTPs outlined in the MITRE ATT&CK framework under privilege escalation techniques, specifically targeting the modification of environment variables to gain unauthorized access or execute code with elevated privileges. Organizations implementing PAM-based authentication systems should consider this vulnerability as part of their broader security posture assessment.
Mitigation strategies for CVE-2010-4708 primarily involve upgrading to Linux-PAM version 1.1.3 or later, where the vulnerability has been addressed through improved file validation and access control mechanisms. System administrators should also implement strict file permissions on .pam_environment files, ensuring that only authorized users can modify these configuration files. Additionally, monitoring for unauthorized modifications to these files and implementing proper access controls on user home directories can help detect and prevent exploitation attempts. Regular security audits of PAM configurations and environment variable handling should be conducted to maintain system integrity and prevent similar vulnerabilities from arising in other components of the authentication framework.