CVE-2010-0832 in Linux
Summary
by MITRE
pam_motd (aka the MOTD module) in libpam-modules before 1.1.0-2ubuntu1.1 in PAM on Ubuntu 9.10 and libpam-modules before 1.1.1-2ubuntu5 in PAM on Ubuntu 10.04 LTS allows local users to change the ownership of arbitrary files via a symlink attack on .cache in a user s home directory, related to "user file stamps" and the motd.legal-notice file.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability described in CVE-2010-0832 represents a critical privilege escalation flaw within the Pluggable Authentication Modules framework on Ubuntu systems. This issue specifically affects the pam_motd module, which is responsible for displaying the Message of the Day and handling user file stamps during authentication processes. The vulnerability stems from inadequate handling of symbolic links in the user's home directory, particularly when the module attempts to create or modify files in the .cache directory. This weakness allows local attackers to manipulate file ownership through carefully crafted symlink attacks, potentially compromising system integrity and user data.
The technical exploitation of this vulnerability occurs through a race condition involving file creation and symbolic link manipulation. When users authenticate through PAM, the pam_motd module creates user file stamps in the .cache directory within the user's home folder. The flaw arises because the module does not properly validate the target of file operations, allowing attackers to establish symbolic links that point to sensitive system files. This creates a scenario where the module's file operations inadvertently affect files outside the intended scope, enabling attackers to change ownership of arbitrary files through the .cache directory. The vulnerability specifically targets the motd.legal-notice file and related user file stamp mechanisms, making it particularly dangerous for systems that rely on proper file ownership controls.
From an operational impact perspective, this vulnerability presents a significant security risk for Ubuntu systems running the affected PAM versions. Local users who can access the system can leverage this flaw to escalate privileges and gain unauthorized control over critical system files. The ability to change file ownership opens pathways for attackers to modify system configurations, install malicious software, or establish persistent access mechanisms. This vulnerability directly impacts the principle of least privilege and can lead to complete system compromise when combined with other exploitation techniques. The attack vector is particularly concerning because it requires minimal privileges and can be executed without requiring special permissions or system-level access.
Security mitigations for CVE-2010-0832 primarily involve applying the vendor-provided security patches and updates. Ubuntu users should immediately upgrade to libpam-modules version 1.1.0-2ubuntu1.1 for Ubuntu 9.10 or 1.1.1-2ubuntu5 for Ubuntu 10.04 LTS to resolve the symbolic link handling issues in the pam_motd module. Additionally, system administrators should implement proper file permissions and monitoring for the .cache directory in user home folders to detect potential symlink attacks. The vulnerability aligns with CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) race conditions, and can be mapped to ATT&CK technique T1068, which covers privilege escalation through local exploits. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive monitoring of authentication-related activities for early detection of potential exploitation attempts.