CVE-2012-5223 in vbseo
Summary
by MITRE
The proc_deutf function in includes/functions_vbseocp_abstract.php in vBSEO 3.5.0, 3.5.1, 3.5.2, 3.6.0, and earlier allows remote attackers to insert and execute arbitrary PHP code via "complex curly syntax" in the char_repl parameter, which is inserted into a regular expression that is processed by the preg_replace function with the eval switch.
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Analysis
by VulDB Data Team • 05/26/2025
The vulnerability identified as CVE-2012-5223 represents a critical remote code execution flaw within the vBSEO 3.5.0 through 3.6.0 software suite, specifically targeting the proc_deutf function located in includes/functions_vbseocp_abstract.php. This vulnerability exploits a fundamental weakness in input validation and sanitization mechanisms, allowing malicious actors to inject arbitrary PHP code through a carefully crafted char_repl parameter. The flaw operates by leveraging the preg_replace function with the eval modifier, which creates a dangerous execution path when processing user-supplied input that contains complex curly syntax patterns.
The technical implementation of this vulnerability stems from improper handling of user input within the vBSEO software's text processing functions. When the char_repl parameter is passed to the proc_deutf function, it undergoes no adequate sanitization or validation before being incorporated into a regular expression pattern. The preg_replace function with the /e modifier (eval switch) processes this pattern and executes any PHP code contained within the replacement string, creating a direct path for arbitrary code execution. This pattern aligns with CWE-94, which describes the improper control of generation of code, and specifically relates to CWE-74, which addresses injection flaws. The vulnerability demonstrates a classic case of code injection where user-controllable data is directly interpreted as executable code.
The operational impact of CVE-2012-5223 extends far beyond simple data compromise, as it provides attackers with complete system control over affected installations. Successful exploitation enables remote attackers to execute arbitrary PHP code with the privileges of the web server process, potentially leading to full system compromise, data theft, or service disruption. The vulnerability affects multiple versions of vBSEO, indicating a widespread exposure across the user base, and the nature of the flaw means that any user with access to the affected parameter can exploit it. This creates a significant risk for forum administrators and users who may not be aware of the vulnerability, as the attack vector is accessible through standard web interface interactions. The vulnerability also aligns with ATT&CK technique T1059.007, which covers the use of PHP for command and control activities.
Mitigation strategies for this vulnerability require immediate attention from affected organizations, beginning with the urgent application of vendor patches or updates to vBSEO versions that address this specific flaw. System administrators should implement network-level restrictions and monitoring to detect potential exploitation attempts, particularly focusing on unusual patterns in the char_repl parameter usage. Input validation and sanitization measures should be strengthened at multiple levels, including the implementation of proper escaping for regular expression patterns and removal of the eval modifier from preg_replace operations. Organizations should also consider implementing web application firewalls to filter out malicious payloads targeting this specific vulnerability pattern. The remediation process must include thorough testing of patched environments to ensure that the fix does not introduce regressions in legitimate functionality while maintaining the security posture against similar injection vulnerabilities.