CVE-2008-6849 in phpGreetCards
Summary
by MITRE
Unrestricted file upload vulnerability in index.php in phpGreetCards 3.7 allows remote attackers to execute arbitrary PHP code by uploading a file with an executable extension, then accessing it via a via a link that is listed by userfiles/number_shell.php.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2008-6849 represents a critical unrestricted file upload flaw in phpGreetCards version 3.7 that fundamentally compromises the security posture of affected systems. This vulnerability resides within the index.php script and enables remote attackers to bypass file validation mechanisms by uploading malicious files with executable extensions. The flaw directly violates security principles by allowing unauthorized file execution, creating a pathway for attackers to establish persistent access and execute arbitrary code on the target server. The vulnerability's severity is amplified by the fact that uploaded files are stored in the userfiles directory with predictable naming patterns such as number_shell.php, making exploitation straightforward and automated.
The technical implementation of this vulnerability stems from inadequate input validation and file extension checking mechanisms within the phpGreetCards application. Attackers can upload PHP shell files or other malicious executables with extensions that are not properly filtered or rejected by the application's upload functionality. When these files are stored in the userfiles directory and subsequently accessed through the predictable URL structure userfiles/number_shell.php, they execute with the privileges of the web server process. This represents a classic case of insufficient sanitization and validation of user-supplied data, which falls under the CWE-434 category of Unrestricted Upload of File with Dangerous Type. The vulnerability demonstrates poor secure coding practices where the application fails to implement proper file type verification, access control, or execution restrictions for uploaded content.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with a persistent backdoor into affected systems. Once an attacker successfully uploads a malicious file, they can execute arbitrary commands on the target server, potentially leading to complete system compromise, data exfiltration, or use of the compromised system as a launchpad for further attacks. The vulnerability's accessibility via remote exploitation means that attackers do not require physical access or local credentials to exploit the flaw, making it particularly dangerous in networked environments. The predictable file naming convention userfiles/number_shell.php reduces the complexity of exploitation and enables automated attack tools to target vulnerable systems. This vulnerability aligns with ATT&CK technique T1190 for Exploit Public-Facing Application and T1059 for Command and Scripting Interpreter, as it allows for remote command execution through web-based interfaces.
Mitigation strategies for CVE-2008-6849 must address both the immediate vulnerability and implement comprehensive security controls to prevent similar issues. Organizations should immediately apply the vendor-supplied patches or upgrade to a secure version of phpGreetCards that properly validates file extensions and implements strict upload restrictions. The remediation process requires implementing robust file type validation that rejects executable extensions and enforces content-based verification rather than relying solely on file extension checks. Security controls should include moving uploaded files outside the web root directory, implementing proper access controls, and using randomized naming conventions for uploaded files to prevent predictable URL access patterns. Additionally, organizations should deploy web application firewalls to monitor and block suspicious file upload attempts, implement regular security scanning to identify vulnerable applications, and establish proper input validation mechanisms that align with secure coding practices outlined in OWASP Top Ten and NIST guidelines. The vulnerability underscores the critical importance of defense-in-depth strategies that combine multiple security layers to protect against file upload attacks and other common web application vulnerabilities.