CVE-2004-0992 in Proxytunnel
Summary
by MITRE
Format string vulnerability in the -a option (daemon mode) in Proxytunnel before 1.2.3 allows remote attackers to execute arbitrary code via format string specifiers in an invalid proxy answer.
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Analysis
by VulDB Data Team • 07/01/2021
The vulnerability identified as CVE-2004-0992 represents a critical format string vulnerability within the proxytunnel utility, specifically affecting versions prior to 1.2.3. This flaw exists within the daemon mode implementation when processing the -a option, creating a significant security risk that can be exploited by remote attackers to execute arbitrary code on affected systems. The vulnerability stems from improper input validation and handling of user-supplied data within the proxy tunneling process, particularly when the application encounters invalid proxy responses.
The technical implementation of this vulnerability occurs when proxytunnel operates in daemon mode and processes invalid proxy responses containing format string specifiers. The application fails to properly sanitize or escape user-provided input before using it in printf-style functions, creating a classic format string vulnerability. This flaw allows attackers to inject malicious format specifiers that can lead to information disclosure, stack corruption, and ultimately arbitrary code execution. The vulnerability specifically affects the handling of proxy responses that contain format string characters such as %s, %d, %x, and other printf-compatible specifiers, which are then processed without proper validation.
From an operational perspective, this vulnerability presents a severe threat to systems running vulnerable versions of proxytunnel in daemon mode. Attackers can exploit this weakness to execute arbitrary code with the privileges of the proxytunnel process, which typically runs with elevated permissions to handle network traffic. The impact extends beyond simple code execution to include potential privilege escalation, system compromise, and unauthorized access to network resources. The vulnerability is particularly dangerous in environments where proxytunnel is used to manage network traffic or provide secure communication channels, as it can be leveraged to gain unauthorized access to sensitive network infrastructure.
The exploitability of this vulnerability aligns with common attack patterns documented in the attack framework, where format string vulnerabilities are classified under the MITRE ATT&CK technique T1059.1001 for command and scripting interpreter. The vulnerability also corresponds to CWE-134, which specifically addresses format string vulnerabilities where format strings are constructed using data from external sources without proper validation. Organizations using vulnerable proxytunnel implementations face significant risk of unauthorized system access, data breaches, and potential compromise of entire network segments that rely on the proxy tunneling functionality. The attack surface is particularly broad given that proxytunnel is commonly used in enterprise environments for secure remote access and network connectivity management.
The recommended mitigation strategy involves immediate upgrade to proxytunnel version 1.2.3 or later, which includes proper input validation and sanitization of format string parameters. Additionally, system administrators should implement network segmentation to limit access to proxytunnel services, disable unnecessary daemon modes, and monitor for suspicious network traffic patterns. Security patches should be applied promptly, and organizations should conduct thorough vulnerability assessments to identify all instances of vulnerable proxytunnel installations. The fix typically involves implementing proper input validation routines that sanitize user-supplied data before it is processed through printf-style functions, ensuring that format specifiers are properly escaped or removed to prevent exploitation of the vulnerability.