CVE-2004-2140 in YaBB
Summary
by MITRE
CRLF injection vulnerability in YaBB 1 Gold before 1.3.2 allows remote attackers to modify text file contents via the subject variable.
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Analysis
by VulDB Data Team • 06/20/2019
The CVE-2004-2140 vulnerability represents a critical cross-site scripting and CRLF injection flaw discovered in YaBB 1 Gold versions prior to 1.3.2. This vulnerability specifically targets the subject variable handling within the bulletin board system, creating a pathway for remote attackers to manipulate text file contents through carefully crafted input sequences. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly escape or filter carriage return and line feed characters within user-submitted data.
The technical exploitation of this vulnerability occurs when attackers submit malicious input containing CRLF sequences such as \r\n or %0d%0a into the subject field of forum posts or messages. These sequences, when processed by the vulnerable application, can inject additional headers or modify the content structure of text files stored on the server. The vulnerability operates at the application layer and can be classified under CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers. This weakness enables attackers to manipulate the HTTP response headers or inject malicious content into text files that are subsequently processed by the application.
The operational impact of this vulnerability extends beyond simple content modification, as it can facilitate more sophisticated attacks including session hijacking, cache poisoning, and data corruption within the forum's text-based storage mechanisms. Attackers can exploit this flaw to inject malicious content into log files, configuration text files, or other text-based data stores that the application maintains. The vulnerability's remote nature means that attackers do not require local system access or authentication to exploit the issue, making it particularly dangerous for publicly accessible forum platforms. This weakness aligns with ATT&CK technique T1190, which describes the exploitation of vulnerabilities in web applications to manipulate data and potentially gain further access to systems.
Mitigation strategies for this vulnerability require immediate patching of YaBB 1 Gold installations to version 1.3.2 or later, which includes proper input sanitization and validation. Organizations should implement comprehensive input validation that filters or escapes CRLF characters in all user-submitted data, particularly in fields that are later used in text file operations. The implementation of proper output encoding and the use of secure coding practices that prevent direct insertion of user input into text files without proper sanitization are essential defensive measures. Additionally, network segmentation and monitoring of unusual text file modifications can help detect exploitation attempts. Security teams should also consider implementing web application firewalls that can detect and block CRLF injection patterns, and conduct regular vulnerability assessments to identify similar weaknesses in other applications within the infrastructure that may be susceptible to the same class of attack.