CVE-2005-1193 in phpBB
Summary
by MITRE
The bbencode_second_pass and make_clickable functions in bbcode.php for phpBB before 2.0.15, as used in viewtopic.php, privmsg.php, and other scripts, allow remote attackers to execute arbitrary script via a BBcode tag with a (1) javascript:, (2) applet:, (3) about:, (4) activex:, (5) chrome:, or (6) script: URI scheme, as demonstrated using the URL tag.
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Analysis
by VulDB Data Team • 12/15/2024
The vulnerability identified as CVE-2005-1193 represents a critical cross-site scripting flaw in phpBB versions prior to 2.0.15, specifically within the bbcode.php script that processes BBcode tags in various forum components including viewtopic.php and privmsg.php. This security weakness arises from insufficient input validation and sanitization of BBcode URI schemes, allowing malicious actors to inject dangerous script content through specially crafted BBcode tags. The vulnerability is categorized under CWE-79 as a cross-site scripting attack, where the application fails to properly escape or filter user-supplied input before rendering it in web pages.
The technical implementation of this flaw occurs in the bbencode_second_pass and make_clickable functions which handle the processing of BBcode tags containing URL information. Attackers can exploit this vulnerability by creating BBcode tags that utilize dangerous URI schemes such as javascript:, applet:, about:, activex:, chrome:, or script: which are typically blocked by web browsers for security reasons. When these malicious BBcode tags are processed by the vulnerable phpBB software, the URI schemes are not properly sanitized or filtered, allowing the embedded JavaScript code to execute in the context of other users' browsers. This creates a persistent cross-site scripting attack vector that can be triggered when legitimate users view forum posts containing the malicious BBcode content.
The operational impact of CVE-2005-1193 is significant and far-reaching within the phpBB community, as it enables attackers to perform various malicious activities including session hijacking, credential theft, and redirection to malicious websites. The vulnerability affects all phpBB installations running versions before 2.0.15, making it particularly dangerous given the widespread adoption of this forum software. When exploited, the vulnerability can lead to complete compromise of user sessions, allowing attackers to impersonate legitimate users and potentially gain administrative privileges. The attack vector is particularly insidious because it operates through normal forum functionality, making it difficult for users to distinguish between legitimate and malicious content, and the attack can be executed by any user with posting privileges.
The vulnerability demonstrates a classic case of insufficient output escaping and input validation, which aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter. Organizations using affected phpBB versions should immediately implement the security patch released by phpBB developers addressing this specific vulnerability. The mitigation strategy involves upgrading to phpBB 2.0.15 or later versions where proper URI scheme validation and filtering has been implemented. Additionally, administrators should consider implementing additional security measures such as content filtering, user input validation, and monitoring for suspicious BBcode usage patterns. The vulnerability also highlights the importance of proper security testing and code review processes to identify similar flaws in web applications that process user-generated content, as outlined in the OWASP Top 10 security principles for web application security.