CVE-2005-4135 in SimpleBBS
Summary
by MITRE
Direct static code injection vulnerability in includes/newtopic.php in SimpleBBS 1.1 and earlier allows remote attackers to execute arbitrary commands via shell metacharacters in the Host header (possibly the name parameter or variable), which is then written to data/topics.php.
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Analysis
by VulDB Data Team • 11/23/2025
The vulnerability identified as CVE-2005-4135 represents a critical direct static code injection flaw within SimpleBBS version 1.1 and earlier systems. This vulnerability resides in the includes/newtopic.php script where user-supplied input from the Host header is improperly processed and subsequently written to the data/topics.php file without adequate sanitization or validation measures. The flaw creates a pathway for remote attackers to execute arbitrary commands on the affected system by leveraging shell metacharacters within the Host header parameter, which may also involve the name parameter or variable, effectively allowing attackers to inject malicious code directly into the application's execution flow.
The technical implementation of this vulnerability demonstrates a classic case of input validation failure where the application fails to properly sanitize or escape user-supplied data before incorporating it into system commands or file operations. When the Host header containing shell metacharacters is processed by the newtopic.php script, the application treats this input as executable code rather than as benign data, leading to command injection. This type of vulnerability falls under CWE-94, which specifically addresses "Improper Control of Generation of Code ('Code Injection')" and aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution. The vulnerability's impact is particularly severe because it allows remote code execution without requiring authentication, making it highly attractive to attackers seeking to compromise systems.
The operational implications of this vulnerability extend beyond simple code injection, as it provides attackers with full control over the affected SimpleBBS system. Once exploited, attackers can execute arbitrary commands with the privileges of the web application, potentially leading to complete system compromise, data exfiltration, or the establishment of persistent backdoors. The fact that the vulnerability affects the Host header parameter suggests that it may be exploitable through various attack vectors including HTTP request smuggling, cache poisoning, or direct HTTP header manipulation. The injection occurs in the data/topics.php file, meaning that successful exploitation could result in long-term persistence and data corruption, as the malicious code would be stored and executed whenever the affected topics file is accessed or processed.
Mitigation strategies for CVE-2005-4135 should prioritize immediate patching of the SimpleBBS application to version 1.2 or later, where the vulnerability has been addressed through proper input sanitization and validation mechanisms. Organizations should implement strict input validation on all user-supplied data, particularly headers and parameters that may be processed by the application. The implementation of proper escape sequences and parameter sanitization techniques should be enforced throughout the application codebase to prevent any future injection vulnerabilities. Additionally, network-level protections such as web application firewalls and intrusion detection systems should be configured to monitor for suspicious header patterns and command injection attempts. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities, with particular attention to legacy systems that may contain similar flaws in their input handling mechanisms. The vulnerability serves as a reminder of the critical importance of secure coding practices and the necessity of implementing defense-in-depth strategies to protect against command injection attacks.