CVE-2002-0851 in ISDN4Linux
Summary
by MITRE
Format string vulnerability in ISDN Point to Point Protocol (PPP) daemon (ipppd) in the ISDN4Linux (i4l) package allows local users to gain root privileges via format strings in the device name command line argument, which is not properly handled in a call to syslog.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability described in CVE-2002-0851 represents a critical format string flaw within the ISDN Point to Point Protocol daemon known as ipppd, which is part of the ISDN4Linux package. This daemon serves as a crucial component for establishing and managing ISDN connections, particularly in Linux environments where ISDN networking is implemented. The vulnerability specifically manifests when the daemon processes command line arguments, particularly those related to device names, without proper sanitization of format specifiers. The flaw occurs because the ipppd daemon directly passes user-supplied device name arguments to the syslog function without adequate validation or escaping of format string characters. This creates a classic format string vulnerability where malicious input can contain format specifiers such as %s, %d, or %x that are interpreted by the syslog function, potentially leading to arbitrary code execution or privilege escalation.
The technical exploitation of this vulnerability relies on the daemon's improper handling of user input through the syslog function call, which is a well-documented pattern that aligns with CWE-134, the weakness category for format string vulnerabilities. When a local attacker provides a specially crafted device name argument containing format specifiers, the ipppd daemon processes this input directly through syslog, allowing the attacker to manipulate memory locations, read or write arbitrary data, and ultimately execute code with the privileges of the running daemon. The daemon typically operates with elevated privileges to manage ISDN connections, making this a particularly dangerous vulnerability since successful exploitation would allow attackers to gain root access to the system. This type of vulnerability is classified under the ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation" and specifically addresses local privilege escalation through software vulnerabilities.
The operational impact of this vulnerability extends beyond simple privilege escalation as it affects the fundamental security posture of systems relying on ISDN4Linux for network connectivity. Systems where ipppd is running as a privileged daemon become immediately compromised when an attacker can supply malicious device name arguments, potentially allowing for complete system takeover. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as the attacker only needs local access to the system where the daemon is running. The attack vector is straightforward, involving the manipulation of command line arguments passed to the ipppd daemon, making it an attractive target for attackers who may already have local access through other means. This vulnerability demonstrates the critical importance of input validation and proper argument handling in system daemons, particularly those operating with elevated privileges, as even seemingly benign parameters can become attack vectors when not properly sanitized.
Mitigation strategies for CVE-2002-0851 should focus on immediate patching of the affected ISDN4Linux package to ensure that the ipppd daemon properly handles format strings in command line arguments. Organizations should also implement proper input validation and sanitization mechanisms to prevent format specifiers from being passed directly to syslog functions. The principle of least privilege should be enforced by running the ipppd daemon with minimal necessary privileges, and system administrators should regularly audit running services and their privilege levels. Additionally, monitoring for unusual syslog activity or unauthorized command line argument usage can help detect exploitation attempts. This vulnerability highlights the necessity of following secure coding practices and proper error handling in system-level software components, particularly those that interact with user-supplied input. The remediation process should include comprehensive testing to ensure that patched versions properly handle all format string scenarios while maintaining the intended functionality of the ISDN connection management system. Organizations should also consider implementing network segmentation and access controls to limit local access to systems running vulnerable daemons, reducing the attack surface for such local privilege escalation vulnerabilities.