CVE-2007-5071 in Simple PHP Blog
Summary
by MITRE
Incomplete blacklist vulnerability in upload_img_cgi.php in Simple PHP Blog before 0.5.1 allows remote attackers to upload dangerous files and execute arbitrary code, as demonstrated by a filename ending in .php. or a .htaccess file, a different vector than CVE-2005-2733. NOTE: the vulnerability was also present in a 0.5.1 download available in the early morning of 20070923. NOTE: the original 20070920 disclosure provided an incorrect filename, img_upload_cgi.php.
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Analysis
by VulDB Data Team • 10/30/2017
The vulnerability described in CVE-2007-5071 represents a critical insecure file upload flaw in Simple PHP Blog versions prior to 0.5.1 that enables remote code execution through improper input validation. This vulnerability operates through an incomplete blacklist mechanism in the upload_img_cgi.php script, which fails to properly validate file extensions and content, allowing attackers to bypass security measures and upload malicious files. The flaw specifically manifests when the application processes file uploads without adequate sanitization of filenames, creating a pathway for attackers to execute arbitrary code on the target system. The vulnerability demonstrates characteristics of CWE-434, which addresses insecure file upload vulnerabilities where applications accept files from untrusted sources without proper validation, and aligns with ATT&CK technique T1190 for gaining access through exploitation of vulnerabilities in web applications.
The technical implementation of this vulnerability relies on the application's insufficient validation of uploaded files, particularly focusing on filename extensions and content type checks. Attackers can exploit this by uploading files with extensions that end in .php or .htaccess, which are typically blacklisted but bypassed due to the incomplete validation mechanism. The original disclosure referenced a filename error, indicating that the vulnerability existed in the actual codebase despite the initial incorrect reference to img_upload_cgi.php instead of upload_img_cgi.php. This error in the initial disclosure highlights the importance of proper vulnerability documentation and the potential for confusion in security research when dealing with similar-looking filenames across different versions of applications. The vulnerability's persistence in a 0.5.1 release available on September 23, 2007, demonstrates that the fix was either incomplete or not properly implemented, indicating poor quality assurance in the software development lifecycle.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise, as attackers can upload web shells or other malicious payloads that provide persistent access to the target server. When combined with the web application's file handling mechanisms, this vulnerability enables attackers to execute commands with the privileges of the web server process, potentially leading to data theft, service disruption, or further network infiltration. The attack vector differs from CVE-2005-2733, indicating that this represents a distinct exploitation pathway within the same software family, suggesting that attackers may be able to leverage multiple vulnerabilities within the same application to achieve their objectives. The presence of this vulnerability in multiple versions of the software demonstrates a pattern of security oversight that could be addressed through better input validation and proper security testing procedures.
Mitigation strategies for this vulnerability must address both the immediate code-level issues and broader architectural security concerns. The primary fix involves implementing a comprehensive whitelist-based validation system that only accepts known safe file extensions and content types, rather than relying on incomplete blacklists that can be bypassed. Organizations should also implement proper file type checking using multiple validation methods including MIME type verification, file content analysis, and server-side sanitization of uploaded filenames. Additional security measures include restricting upload directories to prevent execution of uploaded files, implementing proper access controls, and ensuring that uploaded files are stored outside the web root directory. The vulnerability's classification under CWE-434 emphasizes the need for comprehensive file upload validation, while its relationship to ATT&CK techniques demonstrates the importance of network segmentation and monitoring to detect and respond to exploitation attempts. Regular security audits and proper version management practices are essential to prevent such vulnerabilities from persisting in software deployments and to ensure that security fixes are properly implemented and tested before deployment.