CVE-2002-0824 in FreeBSD
Summary
by MITRE
BSD pppd allows local users to change the permissions of arbitrary files via a symlink attack on a file that is specified as a tty device.
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Analysis
by VulDB Data Team • 07/03/2024
The vulnerability identified as CVE-2002-0824 affects the BSD pppd (Point-to-Point Protocol daemon) implementation, specifically targeting the insecure handling of symbolic links during tty device file operations. This flaw represents a classic symlink attack vector that enables local users to manipulate file permissions through carefully crafted symbolic link manipulations. The vulnerability stems from the daemon's failure to properly validate file paths when opening tty devices, creating an opportunity for privilege escalation and unauthorized file access.
The technical implementation of this vulnerability occurs within the pppd daemon's file handling routines where it processes tty device specifications without adequate symlink resolution checks. When the daemon opens a specified tty device file, it does not perform proper validation to ensure the target is a legitimate device file rather than a symbolic link pointing to another location. This weakness allows an attacker to create a symbolic link that points to a sensitive system file, then manipulate the permissions of that target file through the pppd process running with elevated privileges. The flaw aligns with CWE-377, which addresses insecure temporary file handling and improper handling of symbolic links, and specifically relates to CWE-59, which covers improper handling of symbolic links.
Operationally, this vulnerability creates a significant security risk for systems running BSD pppd, as local users can potentially modify permissions of critical system files without proper authorization. The attack requires local access to the system but can result in privilege escalation and unauthorized file manipulation. Attackers could exploit this to modify system configuration files, create backdoors, or gain persistent access to the system. The impact extends beyond simple permission changes, as the compromised daemon process typically runs with elevated privileges, potentially allowing attackers to modify system binaries or establish persistent access mechanisms. This vulnerability directly maps to ATT&CK technique T1068, which covers local privilege escalation through exploitation of system vulnerabilities, and T1548.001, covering abuse of elevated privileges for privilege escalation.
Mitigation strategies for CVE-2002-0824 require immediate system hardening measures including updating to patched versions of BSD pppd, implementing proper file path validation, and restricting symbolic link creation in sensitive directories. System administrators should ensure that pppd is configured to use absolute paths for tty devices and implement proper symlink resolution checks before file operations. The recommended approach involves applying vendor patches that address the specific symlink handling flaw in the daemon's file opening routines. Additionally, implementing mandatory access controls and file integrity monitoring can help detect unauthorized permission changes. Organizations should also consider disabling unnecessary pppd functionality and restricting local user access to system resources that could be exploited through similar symlink attacks. The vulnerability demonstrates the critical importance of proper input validation and secure file handling practices in system daemons, particularly those running with elevated privileges.