CVE-2004-0396 in NetBSD
Summary
by MITRE
Heap-based buffer overflow in CVS 1.11.x up to 1.11.15, and 1.12.x up to 1.12.7, when using the pserver mechanism allows remote attackers to execute arbitrary code via Entry lines.
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Analysis
by VulDB Data Team • 07/12/2025
The vulnerability identified as CVE-2004-0396 represents a critical heap-based buffer overflow affecting the Concurrent Versions System (CVS) version control software. This flaw exists in CVS versions 1.11.x through 1.11.15 and 1.12.x through 1.12.7 when utilizing the pserver authentication mechanism. The vulnerability stems from inadequate input validation within the Entry line processing functionality, which forms part of the CVS protocol implementation for remote repository access. The heap-based nature of this overflow indicates that malicious input can corrupt memory allocated on the heap, potentially leading to arbitrary code execution.
The technical exploitation of this vulnerability occurs through the pserver mechanism, which is CVS's protocol for remote repository access using the standard rsh or ssh protocols. When a client connects to a CVS server using pserver, the server processes Entry lines that contain metadata about files in the repository. Attackers can craft malicious Entry lines containing oversized data that exceeds the allocated buffer space, causing a heap overflow condition. This overflow allows attackers to overwrite adjacent memory locations, potentially corrupting program execution flow and enabling code injection attacks. The vulnerability is particularly dangerous because it allows remote code execution without requiring authentication to the target system, making it an attractive target for attackers seeking to compromise CVS servers.
The operational impact of CVE-2004-0396 extends beyond simple code execution, as it can lead to complete system compromise when exploited successfully. Organizations relying on CVS for version control and source code management face significant risk when running vulnerable versions of the software. The vulnerability affects systems where CVS servers are accessible over networks, particularly those exposed to untrusted clients or networks. Attackers can leverage this vulnerability to gain unauthorized access to source code repositories, potentially accessing sensitive information, modifying code, or establishing persistent backdoors. The attack vector does not require authentication to the target system, making it particularly concerning for organizations with public CVS servers or those with weak network segmentation.
This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation in network services. From an ATT&CK framework perspective, this vulnerability maps to T1190 - Exploit Public-Facing Application and T1059 - Command and Scripting Interpreter, as it enables remote code execution through exploitation of a public-facing service. The exploitation pattern follows typical attack methodologies where attackers target services with known vulnerabilities to establish initial access. Organizations should consider this vulnerability as part of a broader threat landscape where outdated version control systems become entry points for more sophisticated attacks. The vulnerability demonstrates the critical importance of keeping version control systems updated and implementing proper network segmentation to limit exposure of such services to untrusted networks. Mitigation strategies should include immediate patching of affected systems, network monitoring for exploitation attempts, and implementation of access controls to limit exposure of CVS servers to trusted networks only.
The remediation approach for CVE-2004-0396 requires immediate deployment of patches provided by the CVS development team, specifically updating to versions that address the heap overflow in Entry line processing. Organizations should also implement network-level controls such as firewall rules to restrict access to CVS pserver ports, typically port 2401, to trusted IP addresses only. Additionally, monitoring for unusual Entry line patterns or malformed requests can help detect exploitation attempts. The vulnerability serves as a reminder of the critical importance of vulnerability management programs and the need for regular security assessments of all network services, particularly those handling user input from remote locations.