CVE-2008-3970 in Pam Mount
Summary
by MITRE
pam_mount 0.10 through 0.45, when luserconf is enabled, does not verify mountpoint and source ownership before mounting a user-defined volume, which allows local users to bypass intended access restrictions via a local mount.
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Analysis
by VulDB Data Team • 08/17/2019
The vulnerability identified as CVE-2008-3970 affects pam_mount versions 0.10 through 0.45 and represents a critical authorization bypass flaw within the Pluggable Authentication Modules mounting subsystem. This issue specifically manifests when the luserconf configuration option is enabled, creating a scenario where the system fails to properly validate the ownership and permissions of mountpoints and source locations before executing user-defined volume mounting operations. The flaw resides in the authentication and authorization mechanisms that govern how user sessions interact with file system mounting capabilities through the pam_mount module.
The technical implementation of this vulnerability stems from insufficient input validation and privilege escalation within the pam_mount component's codebase. When luserconf is enabled, users can define their own mount configurations through configuration files, but the system does not perform adequate checks to ensure that these mountpoints and source locations are properly owned by the appropriate user or group. This omission allows local attackers to manipulate mount configurations to access resources that should be restricted to specific users or groups, effectively bypassing the intended access controls that protect system resources. The vulnerability operates at the intersection of user session management and file system access control, leveraging the trust model inherent in the pam_mount framework.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader system security implications. Local users who can manipulate the mount configuration files can potentially access sensitive data, mount volumes from unauthorized sources, or create mountpoints that provide access to restricted directories. This flaw particularly affects systems where pam_mount is used for automatic mounting of user home directories or network file systems, as it undermines the security boundaries that separate user sessions and system resources. The vulnerability aligns with CWE-284, which addresses improper access control, and represents a classic example of insufficient privilege checking in security-critical components.
Mitigation strategies for this vulnerability require immediate attention through system updates to pam_mount versions that address the ownership verification flaw. Administrators should disable luserconf functionality when it is not strictly required, as this option directly enables the vulnerable behavior. Additionally, proper file system permissions and ownership controls should be enforced on pam_mount configuration files to prevent unauthorized modifications. The remediation process should include comprehensive auditing of existing mount configurations and verification that all mountpoints and source locations have appropriate ownership and access controls. Security monitoring should be implemented to detect unauthorized changes to mount configuration files, and system administrators should consider implementing additional layers of access control through SELinux or AppArmor policies to further restrict the impact of potential exploitation attempts. This vulnerability demonstrates the critical importance of proper input validation and access control verification in authentication and authorization subsystems, particularly those that operate with elevated privileges and direct file system access capabilities.