CVE-2000-0950 in Firewall Toolkit
Summary
by MITRE
Format string vulnerability in x-gw in TIS Firewall Toolkit (FWTK) allows local users to execute arbitrary commands via a malformed display name.
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Analysis
by VulDB Data Team • 04/06/2019
The vulnerability identified as CVE-2000-0950 represents a critical format string flaw within the x-gw component of the TIS Firewall Toolkit, a widely deployed network security solution in the late 1990s and early 2000s. This vulnerability resides in the display name handling functionality of the x-gw daemon, which serves as a graphical user interface component for managing firewall rules and configurations. The flaw manifests when the system processes user-supplied display names that contain format specifiers such as %s, %d, or %x, which are typically used in printf-style functions to format output strings. When these maliciously crafted strings are processed without proper validation or sanitization, they can trigger unintended behavior in the underlying printf function calls. The vulnerability is classified as a local privilege escalation issue because it requires local system access to exploit, though the potential for arbitrary code execution makes it particularly dangerous in environments where local users might have elevated privileges or where the system is misconfigured.
The technical exploitation of this vulnerability follows a classic format string attack pattern where an attacker crafts a malicious display name containing format specifiers that reference memory locations on the stack. When the x-gw component processes this malformed input, it passes the unvalidated string directly to a printf function, allowing the attacker to read arbitrary memory locations or potentially overwrite critical memory segments. This type of vulnerability is categorized under CWE-134, which specifically addresses the use of format strings in functions like printf without proper validation. The attack vector leverages the fact that the x-gw component does not properly sanitize user input before using it in printf-style formatting operations, creating a path for memory corruption that can be exploited to execute arbitrary code with the privileges of the x-gw process. The operational impact is significant as the x-gw daemon typically runs with elevated privileges to manage firewall configurations, making successful exploitation potentially devastating for the entire network security infrastructure.
The broader implications of this vulnerability extend beyond simple local privilege escalation, as it represents a fundamental flaw in input validation and string handling within security-critical applications. Organizations using TIS Firewall Toolkit in production environments would have been particularly vulnerable to this attack, especially if local users had access to systems running the x-gw daemon. The vulnerability demonstrates how seemingly innocuous user interface components can harbor critical security flaws that undermine the entire security posture of a system. From an operational perspective, this flaw would have been particularly dangerous in enterprise environments where firewall management interfaces are frequently accessed by multiple users, creating potential attack surfaces for both insider threats and compromised accounts. The vulnerability also highlights the importance of proper input validation and the dangers of relying on unsafe string handling functions in security-critical applications.
Mitigation strategies for CVE-2000-0950 should focus on immediate patching of the TIS Firewall Toolkit components, particularly addressing the x-gw daemon's handling of user-supplied display names. System administrators should implement strict input validation for all user-provided data, ensuring that format specifiers are properly escaped or removed before any string processing occurs. The recommended approach aligns with ATT&CK technique T1059.007 for command and script injection, where the mitigation involves preventing the execution of untrusted code through proper input sanitization. Organizations should also consider implementing network segmentation to limit local access to systems running the vulnerable x-gw component, reducing the attack surface for local privilege escalation attempts. Additionally, regular security audits should verify that no other components within the firewall toolkit exhibit similar format string vulnerabilities, as this type of flaw often indicates broader code quality issues. The vulnerability underscores the necessity of following secure coding practices such as those recommended in the CERT C Secure Coding Standard, which specifically addresses format string vulnerabilities in the context of printf and related functions.