CVE-2004-1315 in phpBB
Summary
by MITRE
viewtopic.php in phpBB 2.x before 2.0.11 improperly URL decodes the highlight parameter when extracting words and phrases to highlight, which allows remote attackers to execute arbitrary PHP code by double-encoding the highlight value so that special characters are inserted into the result, which is then processed by PHP exec, as exploited by the Santy.A worm.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability described in CVE-2004-1315 represents a critical security flaw in phpBB version 2.x prior to 2.0.11 that stems from improper handling of URL decoding during the processing of highlight parameters. This issue occurs within the viewtopic.php script which is responsible for displaying forum topics and managing user interactions. The vulnerability specifically targets the mechanism used to highlight search terms or specific phrases within forum posts, creating a path for remote code execution through carefully crafted input manipulation.
The technical flaw manifests when the application processes the highlight parameter without proper sanitization of URL-encoded values. Attackers can exploit this by double-encoding malicious input where special characters are inserted into the decoded result. This double-encoding technique bypasses initial input validation checks while ensuring that the final processed value contains executable PHP code sequences. When the application subsequently processes this malformed highlight parameter through PHP exec functions, it executes arbitrary commands on the affected server with the privileges of the web application.
This vulnerability directly relates to CWE-185, which covers improper handling of regular expression special characters, and CWE-94, which addresses improper control of generation of code. The exploitation mechanism aligns with ATT&CK technique T1059.007, which involves the use of scripting, and T1078.004, which covers legitimate credentials. The Santy.A worm specifically demonstrated how this vulnerability could be weaponized to create a self-replicating malware that could spread across phpBB installations without requiring user interaction.
The operational impact of CVE-2004-1315 is severe as it allows attackers to gain complete control over affected phpBB installations. Once exploited, attackers can execute arbitrary commands on the server, potentially leading to data theft, service disruption, or further compromise of the network infrastructure. The vulnerability affects not just individual forums but entire networks of phpBB installations, making it particularly dangerous for organizations that rely on this forum software for communication. The fact that the exploit works through simple URL manipulation means that attackers can launch attacks without requiring any special tools or extensive technical knowledge.
Mitigation strategies for this vulnerability include immediate upgrading to phpBB 2.0.11 or later versions where the issue has been patched. Organizations should also implement proper input validation and sanitization mechanisms for all user-supplied data, particularly parameters processed through PHP execution functions. The fix involves ensuring that URL decoding occurs safely and that special characters are properly escaped or filtered before any processing. Network-level protections such as web application firewalls can provide additional defense in depth, though the primary solution remains the official software update. Regular security audits and monitoring of forum installations for unauthorized modifications should also be implemented to detect potential exploitation attempts.