CVE-2015-0868 in Bu2 Bbs
Summary
by MITRE
Unrestricted file upload vulnerability in Mrs. Shiromuku Perl CGI shiromuku(bu2)BBS before 2.91 allows remote attackers to execute arbitrary code by uploading an executable file.
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Analysis
by VulDB Data Team • 04/02/2018
The CVE-2015-0868 vulnerability represents a critical unrestricted file upload flaw in the Mrs. Shiromuku Perl CGI shiromuku(bu2)BBS software version 2.91 and earlier. This vulnerability resides in the web-based bulletin board system's file upload functionality, which fails to properly validate or sanitize file types submitted by remote attackers. The vulnerability stems from inadequate input validation mechanisms that permit malicious users to bypass security restrictions and upload executable files to the target system. The flaw exists within the application's file handling logic where it does not adequately verify the file extension, MIME type, or file content before storing uploaded files on the web server. This oversight creates a path for attackers to upload malicious scripts or binaries that can be executed within the context of the web server, potentially leading to complete system compromise. The vulnerability is particularly dangerous because it allows remote code execution without requiring authentication or privileged access, making it an attractive target for automated exploitation tools and malicious actors seeking to gain unauthorized access to affected systems.
The technical exploitation of CVE-2015-0868 follows a well-established pattern of web application attacks where attackers leverage the lack of proper file validation to upload malicious payloads. When an attacker uploads a file through the vulnerable BBS interface, the system stores the file without performing adequate checks to determine if it contains executable code or malicious content. The vulnerability aligns with CWE-434, which specifically addresses "Unrestricted Upload of File with Dangerous Type," a common weakness in web applications that fail to restrict file uploads to safe formats. This weakness enables attackers to upload files such as perl scripts, php shells, or other executable content that can be executed by the web server when accessed through a browser. The exploitation process typically involves crafting a malicious file with a legitimate-looking extension but containing malicious code, then uploading it through the vulnerable web interface. Once uploaded, the attacker can trigger execution by accessing the file through the web server, potentially gaining shell access or other elevated privileges depending on the web server configuration and permissions.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass broader security implications for affected organizations. Systems running vulnerable versions of Mrs. Shiromuku BBS become potential entry points for attackers seeking to establish persistent access to networks, harvest sensitive data, or use compromised systems as launch points for further attacks. The vulnerability creates a direct pathway for attackers to execute arbitrary commands on the target system, potentially allowing them to install backdoors, modify system files, or access database contents. Organizations using this software may face significant security breaches, data loss, or compliance violations depending on the nature of information stored on the affected systems. The vulnerability also increases the attack surface for lateral movement within networks, as compromised systems can serve as staging areas for attacks against other connected systems. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1190 (Exploit Public-Facing Application) and T1059 (Command and Scripting Interpreter), demonstrating how the initial compromise can lead to further system compromise and data exfiltration activities.
Mitigation strategies for CVE-2015-0868 require both immediate and long-term security measures to address the root cause of the vulnerability. The primary remediation involves upgrading to version 2.91 or later of the Mrs. Shiromuku BBS software, which includes proper file validation and sanitization mechanisms. Organizations should also implement additional security controls such as restricting file upload capabilities, implementing strict file type validation, and using content inspection tools to detect potentially malicious uploads. Web application firewalls and intrusion detection systems can help identify and block suspicious upload attempts, while proper file permissions and secure storage practices can limit the impact of successful exploitation attempts. Security teams should conduct thorough vulnerability assessments to identify all systems running vulnerable versions of the software and ensure that proper patch management procedures are in place. Additional defensive measures include implementing least privilege access controls for file upload directories, monitoring upload activities for suspicious patterns, and establishing incident response procedures to quickly address potential exploitation attempts. Regular security testing and code reviews should be performed to identify similar vulnerabilities in other applications and ensure that file upload functionality is properly secured against future threats.