CVE-2011-4122 in FreeBSD
Summary
by MITRE
Directory traversal vulnerability in openpam_configure.c in OpenPAM before r478 on FreeBSD 8.1 allows local users to load arbitrary DSOs and gain privileges via a .. (dot dot) in the service_name argument to the pam_start function, as demonstrated by a .. in the -c option to kcheckpass.
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Analysis
by VulDB Data Team • 06/26/2024
The vulnerability described in CVE-2011-4122 represents a critical directory traversal flaw within the OpenPAM authentication framework on FreeBSD systems. This issue affects OpenPAM versions prior to revision r478 and specifically targets the openpam_configure.c component, which handles configuration file processing during the PAM authentication workflow. The vulnerability manifests when the pam_start function processes service_name arguments that contain directory traversal sequences, creating a pathway for malicious exploitation that can compromise system security through privilege escalation.
The technical implementation of this vulnerability stems from inadequate input validation within the PAM configuration parsing mechanism. When a local user provides a service_name argument containing .. (dot dot) sequences in the service_name parameter to pam_start, the system fails to properly sanitize these path traversal characters. This allows attackers to bypass normal file access controls and load arbitrary dynamic shared objects from unexpected locations within the filesystem. The vulnerability is particularly dangerous because it operates at the privilege level of the PAM framework itself, which typically runs with elevated permissions necessary for authentication operations.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable complete system compromise. Attackers can leverage this flaw to load malicious DSOs that execute arbitrary code with the privileges of the PAM service, which often includes root-level access. The demonstration using the kcheckpass utility with a .. in the -c option illustrates how this vulnerability can be exploited in real-world scenarios where authentication services are invoked with user-supplied parameters. This creates a persistent threat vector that can be exploited repeatedly by local users who have access to the system but lack administrative privileges.
This vulnerability maps directly to CWE-22 Directory Traversal and aligns with ATT&CK techniques involving privilege escalation and persistence. The weakness represents a classic input validation failure that allows attackers to manipulate file system access patterns and gain unauthorized code execution capabilities. Organizations should immediately apply the relevant security patches for OpenPAM versions prior to r478 and conduct comprehensive audits of their authentication frameworks to identify similar vulnerabilities in other PAM implementations. System administrators should also implement monitoring for suspicious PAM service usage patterns and ensure that all authentication services properly validate input parameters to prevent similar directory traversal attacks from compromising system integrity.