CVE-2003-0787 in OpenSSH
Summary
by MITRE
The PAM conversation function in OpenSSH 3.7.1 and 3.7.1p1 interprets an array of structures as an array of pointers, which allows attackers to modify the stack and possibly gain privileges.
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Analysis
by VulDB Data Team • 07/15/2024
The vulnerability identified as CVE-2003-0787 represents a critical stack-based buffer overflow in the Pluggable Authentication Modules conversation function within OpenSSH versions 3.7.1 and 3.7.1p1. This flaw stems from a fundamental misinterpretation of data structures during the authentication process, where the system incorrectly treats an array of structures as an array of pointers. The vulnerability exists within the authentication framework that governs how OpenSSH handles user credentials and access control, making it particularly dangerous for systems relying on secure remote access protocols.
The technical implementation of this vulnerability exploits a classic stack corruption mechanism through improper memory management. When the PAM conversation function processes authentication requests, it fails to properly validate the structure of input data, causing the system to dereference memory locations incorrectly. This misinterpretation allows malicious actors to manipulate the stack layout and potentially overwrite critical memory segments including return addresses and function pointers. The flaw specifically aligns with CWE-121, which categorizes stack-based buffer overflow conditions, and demonstrates how improper pointer handling can lead to arbitrary code execution. The vulnerability operates at the kernel level authentication interface, where the stack-based memory corruption can be leveraged to execute malicious code with elevated privileges.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise. Attackers can exploit this weakness to gain unauthorized access to systems running vulnerable versions of OpenSSH, potentially leading to data breaches, lateral movement within networks, and persistent access. The vulnerability affects systems where SSH authentication is utilized for remote access, including servers, network devices, and enterprise infrastructure. Given that OpenSSH was widely deployed across Unix-like systems, the potential attack surface was extensive, making this vulnerability particularly dangerous in enterprise environments where SSH serves as the primary remote access protocol. The vulnerability also maps to ATT&CK technique T1565.001, which covers "Data Manipulation" through privilege escalation, and T1078, which covers "Valid Accounts" exploitation.
Mitigation strategies for CVE-2003-0787 require immediate patching of affected OpenSSH installations to version 3.7.1p2 or later, which contains the necessary fixes for the memory handling error. System administrators should also implement network segmentation and access controls to limit exposure, while monitoring for suspicious authentication patterns that might indicate exploitation attempts. Additional defensive measures include disabling unnecessary SSH services, implementing strong authentication mechanisms, and maintaining comprehensive audit logs for security monitoring. Organizations should also consider implementing intrusion detection systems that can identify anomalous authentication behaviors and potential exploitation attempts. The fix implemented in subsequent versions addresses the core issue by ensuring proper memory structure interpretation and implementing bounds checking to prevent the stack corruption that enabled privilege escalation.