CVE-2010-3853 in Linux-PAM
Summary
by MITRE
pam_namespace.c in the pam_namespace module in Linux-PAM (aka pam) before 1.1.3 uses the environment of the invoking application or service during execution of the namespace.init script, which might allow local users to gain privileges by running a setuid program that relies on the pam_namespace PAM check, as demonstrated by the sudo program.
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Analysis
by VulDB Data Team • 10/13/2021
The vulnerability described in CVE-2010-3853 resides within the pam_namespace module of Linux-PAM versions prior to 1.1.3, representing a critical privilege escalation flaw that exploits the insecure handling of environment variables during namespace initialization. This issue specifically affects the pam_namespace.c component which is responsible for managing user namespaces and their associated environment configurations. The flaw manifests when the module executes namespace.init scripts using the environment context of the invoking application or service rather than maintaining a clean, isolated execution environment. This design weakness creates a pathway for local attackers to manipulate the execution context and potentially elevate their privileges through carefully crafted setuid programs that depend on the pam_namespace PAM check.
The technical exploitation of this vulnerability occurs when a setuid program such as sudo invokes the pam_namespace module to establish a namespace environment. Due to the improper environment handling, the namespace.init script inherits variables from the calling process, which may contain maliciously crafted environment values. Attackers can leverage this by placing malicious code or manipulating environment variables such as PATH, LD_LIBRARY_PATH, or other critical variables that influence script execution. The vulnerability is particularly dangerous because it allows local users to bypass normal privilege restrictions, as the executing namespace.init script operates with elevated privileges due to the setuid nature of the calling program. This creates a direct vector for privilege escalation where the attacker's malicious environment variables can be executed within the privileged context of the namespace initialization process.
The operational impact of CVE-2010-3853 extends beyond simple privilege escalation to encompass potential system compromise and persistent access. When exploited successfully, this vulnerability allows attackers to execute arbitrary code with elevated privileges, potentially enabling them to modify system files, install backdoors, or establish persistent access mechanisms. The vulnerability affects any system utilizing Linux-PAM versions before 1.1.3 with pam_namespace enabled, making it particularly concerning for enterprise environments where sudo and other setuid programs are commonly used for administrative tasks. The exploitability of this vulnerability is heightened in environments where users have the ability to execute programs that trigger the pam_namespace module, as the attack surface includes not just system administrators but any local user who can leverage the affected PAM configuration.
Mitigation strategies for CVE-2010-3853 primarily focus on upgrading to Linux-PAM version 1.1.3 or later, which contains the necessary patches to address the environment variable handling issue. Organizations should also implement strict PAM configuration reviews to ensure that pam_namespace is not unnecessarily enabled in environments where it is not required for legitimate operations. The principle of least privilege should be enforced by limiting the use of setuid programs and carefully auditing their configurations. Additionally, system administrators should monitor for unauthorized modifications to namespace.init scripts and implement proper file permissions to prevent tampering. From a security control perspective, this vulnerability aligns with CWE-256 and CWE-78, representing insecure environment handling and command injection vulnerabilities respectively, and can be addressed through controls that align with ATT&CK technique T1068 which covers privilege escalation through local exploits. Organizations should also consider implementing runtime monitoring solutions that can detect anomalous environment variable usage patterns that might indicate exploitation attempts.