CVE-2005-0673 in phpBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in usercp_register.php for phpBB 2.0.13 allows remote attackers to inject arbitrary web script or HTML by setting the (1) allowhtml, (2) allowbbcode, or (3) allowsmilies parameters to inject HTML into signatures for personal messages, possibly when they are processed by privmsg.php or viewtopic.php.
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Analysis
by VulDB Data Team • 07/01/2021
The vulnerability described in CVE-2005-0673 represents a classic cross-site scripting flaw within the phpBB 2.0.13 forum software, specifically targeting the user control panel registration component. This issue arises from inadequate input validation and sanitization mechanisms within the usercp_register.php file, which processes user registration and profile modification parameters. The vulnerability affects the core functionality of the forum's signature management system, where users can configure their personal message signatures to include HTML content. The flaw manifests when attackers manipulate three specific parameters - allowhtml, allowbbcode, and allowsmilies - which control the formatting capabilities available to users when creating their signatures. These parameters determine whether HTML tags, bbcode markup, or smiley faces are processed and displayed within user-generated content.
The technical exploitation of this vulnerability occurs through the manipulation of user input fields that are subsequently processed by the phpBB application's internal parsing mechanisms. When users set these parameters to enable HTML processing, the application fails to properly sanitize or escape the input before rendering it in the context of personal messages or signatures. This creates an environment where malicious actors can inject arbitrary HTML or JavaScript code that executes in the browsers of other forum users who view the affected content. The vulnerability is particularly dangerous because it leverages the legitimate functionality of the forum's signature system, making it difficult to distinguish between benign and malicious content at runtime. The attack vector is facilitated through the processing of messages by privmsg.php and viewtopic.php scripts, which are responsible for displaying private messages and forum topics respectively, creating multiple potential entry points for XSS execution.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it enables attackers to execute persistent malicious code within the context of authenticated forum sessions. This opens the door to session hijacking, credential theft, and the potential for privilege escalation within the forum environment. Users who view affected signatures or messages may unknowingly execute malicious scripts that can capture their session cookies, redirect them to phishing sites, or perform actions on their behalf within the forum. The vulnerability particularly affects forum administrators and regular users who may inadvertently click on malicious links or view compromised signatures. The attack can be executed without requiring special privileges or direct access to the forum's administrative systems, making it a significant threat to forum security and user privacy. This type of vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and represents a common vector for advanced persistent threats in web-based environments.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input sanitization and output encoding mechanisms throughout the phpBB application. The most effective approach involves ensuring that all user-supplied input, particularly HTML content, is properly escaped or filtered before being stored or rendered in web pages. This includes implementing strict validation of the allowhtml, allowbbcode, and allowsmilies parameters to prevent malicious content injection. Organizations should also consider implementing Content Security Policy (CSP) headers to limit the execution of inline scripts and restrict the sources from which content can be loaded. Additionally, regular security updates and patches should be applied to ensure that known vulnerabilities are addressed promptly. The implementation of web application firewalls and intrusion detection systems can provide additional layers of protection by monitoring for suspicious input patterns and blocking known malicious payloads. This vulnerability demonstrates the critical importance of secure coding practices and input validation, as outlined in the OWASP Top Ten and MITRE ATT&CK framework, particularly in the context of web application security and user input handling.