CVE-2006-4889 in SignKorn Guestbook
Summary
by MITRE
Multiple PHP remote file inclusion vulnerabilities in Telekorn SignKorn Guestbook (SL) 1.3 and earlier, when register_globals is enabled, allow remote attackers to execute arbitrary PHP code via a URL in the dir_path parameter in (1) index.php, (2) includes/functions.gb.php, (3) includes/functions.admin.php, (4) includes/admin.inc.php, (5) help.php, (6) smile.php, (7) entry.php; (8) adminhelp0.php, (9) adminhelp1.php, (10) adminhelp2.php, and (11) adminhelp3.php in (a) help/en and (b) help/de directories; and the (12) preview.php, (13) log.php, (14) index.php, (15) config.php, and (16) admin.php in the (c) admin directory, a different set of vectors than CVE-2006-4788.
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Analysis
by VulDB Data Team • 09/23/2017
The vulnerability described in CVE-2006-4889 represents a critical remote file inclusion flaw affecting Telekorn SignKorn Guestbook version 1.3 and earlier systems. This vulnerability specifically exploits the insecure handling of user-supplied input when the PHP configuration parameter register_globals is enabled, creating a pathway for malicious actors to execute arbitrary code on affected systems. The flaw manifests across multiple entry points within the application's codebase, demonstrating the widespread nature of the vulnerability and its potential for extensive exploitation.
The technical implementation of this vulnerability stems from the application's failure to properly validate and sanitize input parameters, particularly the dir_path parameter that is used to include various PHP files throughout the guestbook system. When register_globals is enabled, PHP automatically creates global variables from request data, which means that user-supplied values can directly influence the execution flow of the application. Attackers can manipulate the dir_path parameter to point to malicious remote URLs, causing the application to include and execute arbitrary PHP code hosted on external servers. This vulnerability operates under CWE-88, which categorizes improper neutralization of special elements used in an OS command, specifically applying to the context of remote file inclusion attacks where external URLs are incorporated into system execution paths.
The operational impact of this vulnerability is severe and multifaceted, as it allows remote attackers to gain complete control over affected systems. Once exploited, attackers can execute arbitrary commands, upload malicious files, establish persistent backdoors, and potentially use the compromised system as a launch point for further attacks within the network. The vulnerability affects multiple files across different directories, including administrative components and help documentation files, indicating that the attack surface is extensive and that the exploitation could occur through various access points. This wide-ranging impact makes the vulnerability particularly dangerous as it provides multiple potential vectors for initial compromise and lateral movement within target environments.
The attack pattern for this vulnerability follows the typical remote file inclusion methodology outlined in the MITRE ATT&CK framework, specifically mapping to techniques involving remote code execution through web application vulnerabilities. The exploitation requires minimal prerequisites beyond having register_globals enabled, which was a common configuration in many PHP environments during that era. Organizations should note that this vulnerability operates differently from CVE-2006-4788, suggesting that the security community identified distinct attack vectors within the same software ecosystem. The presence of multiple vulnerable files across different directories indicates that the application's architecture lacked proper input validation and secure coding practices, particularly in how it handles file inclusion operations and parameter processing.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates to versions that address the file inclusion flaws, proper configuration of PHP settings to disable register_globals, and implementation of robust input validation mechanisms. Network-level protections including web application firewalls and proper access controls can provide additional defense-in-depth measures. Organizations should also implement comprehensive code review processes to identify similar patterns and ensure that all file inclusion operations properly validate and sanitize input parameters to prevent similar vulnerabilities from emerging in future development cycles. The vulnerability serves as a critical reminder of the importance of secure coding practices and proper input validation in preventing remote code execution attacks.