CVE-2008-0153 in Pragma TelnetServer
Summary
by MITRE
telnetd.exe in Pragma TelnetServer 7.0.4.589 allows remote attackers to cause a denial of service (process crash and resource exhaustion) via a crafted TELOPT PRAGMA LOGON telnet option, which triggers a NULL pointer dereference.
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Analysis
by VulDB Data Team • 01/14/2025
The vulnerability identified as CVE-2008-0153 affects the telnetd.exe component within Pragma TelnetServer version 7.0.4.589, representing a critical security flaw that enables remote attackers to execute denial of service attacks against affected systems. This vulnerability specifically targets the telnet server implementation and exploits a weakness in how the server handles certain telnet options during the authentication process. The flaw manifests when a maliciously crafted TELOPT PRAGMA LOGON telnet option is transmitted to the server, causing the system to crash and consume excessive resources. The technical root cause of this vulnerability stems from inadequate input validation and error handling within the telnet server's option processing mechanism.
The underlying technical flaw constitutes a NULL pointer dereference condition that occurs when the telnet server attempts to process the specially crafted PRAGMA LOGON telnet option. This type of vulnerability falls under the CWE-476 category, which specifically addresses NULL pointer dereference issues in software implementations. When the telnet server receives the malformed option, it attempts to access memory locations that have not been properly initialized or allocated, resulting in an immediate process crash. The vulnerability demonstrates characteristics consistent with the ATT&CK technique T1499.004, which involves network denial of service attacks that target system resources and availability. The NULL pointer dereference represents a fundamental programming error where the application fails to properly validate input data before attempting to dereference pointers, leading to unpredictable behavior and system instability.
The operational impact of this vulnerability extends beyond simple service disruption, as it can lead to complete system unavailability and resource exhaustion that affects legitimate users and network operations. Remote attackers can exploit this weakness without requiring authentication credentials, making the attack surface particularly broad and dangerous for any organization relying on the affected telnet server implementation. The vulnerability's potential for resource exhaustion means that even a single successful attack can cause sustained service degradation, as the server process may need to be manually restarted and system resources may remain consumed for extended periods. Organizations utilizing this specific version of Pragma TelnetServer face significant risk of operational disruption, particularly in environments where telnet services are critical for administrative access or legacy system integration. The vulnerability also represents a potential vector for broader network compromise, as the service disruption can impact downstream systems that depend on the availability of telnet services for their operations.
Mitigation strategies for this vulnerability should prioritize immediate patching of the affected Pragma TelnetServer software to version 7.0.4.590 or later, which contains the necessary fixes for the NULL pointer dereference issue. Network administrators should implement temporary network segmentation or access controls to restrict telnet service access until the patch is applied, particularly in environments where the service is exposed to untrusted networks. The implementation of intrusion detection systems that can identify and alert on suspicious telnet option sequences may provide additional protection against exploitation attempts. Organizations should also consider implementing alternative authentication and remote access solutions that do not rely on potentially vulnerable telnet implementations, particularly given the known security issues with telnet protocols in modern network environments. The vulnerability serves as a reminder of the importance of proper input validation and error handling in network services, aligning with security best practices outlined in various industry standards including those from the National Institute of Standards and Technology and the Center for Internet Security. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network services and applications that may be susceptible to similar NULL pointer dereference conditions.