CVE-2007-3208 in YaBB
Summary
by MITRE
CRLF injection vulnerability in Yet another Bulletin Board (YaBB) 2.1 allows remote attackers to obtain administrative access via requests to (1) register.pl or (2) profile.pl that write CRLF sequences to a .vars file. NOTE: this can be leveraged to execute arbitrary code.
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Analysis
by VulDB Data Team • 08/12/2022
The CVE-2007-3208 vulnerability represents a critical cross-site scripting and code execution flaw within the Yet another Bulletin Board version 2.1 web application. This vulnerability stems from improper input validation and sanitization mechanisms that fail to properly escape or filter carriage return and line feed characters within user-supplied data. The flaw specifically affects the registration and profile management functionalities of the bulletin board system, where user inputs are directly written to .vars configuration files without adequate security controls. The vulnerability operates through a classic CRLF injection attack vector where maliciously crafted input containing carriage return and line feed sequences can manipulate the application's file writing behavior. When users submit data through the vulnerable register.pl or profile.pl scripts, the application processes these inputs without proper sanitization, allowing attackers to inject CRLF sequences that alter the structure of the target .vars file. This manipulation creates a pathway for attackers to inject malicious code or manipulate application configuration data, ultimately enabling unauthorized administrative access to the bulletin board system.
The technical exploitation of this vulnerability follows a well-documented pattern that aligns with CWE-117, which describes improper output neutralization for logs, and CWE-94, which addresses insufficient control of generation of code. Attackers can leverage this weakness by crafting specially formatted input strings that include CRLF sequences such as %0d%0a or \r\n, which when processed by the vulnerable application, result in the injection of additional lines into the .vars file. The injection process allows attackers to manipulate file contents in ways that can include adding new administrative accounts, modifying existing user permissions, or injecting malicious code that executes within the application context. This type of vulnerability represents a serious security flaw that enables attackers to achieve privilege escalation and persistent access to the system. The vulnerability's potential for arbitrary code execution makes it particularly dangerous as it can be used to establish backdoors, exfiltrate data, or further compromise the underlying infrastructure. The attack vector demonstrates the classic characteristics of a server-side request forgery vulnerability that operates through user input fields, making it particularly challenging to detect and prevent.
The operational impact of CVE-2007-3208 extends beyond simple privilege escalation to encompass full system compromise and potential data breaches. Once an attacker gains administrative access through this vulnerability, they can manipulate the bulletin board's core functionality, modify user permissions, and potentially access sensitive information stored within the application's database or configuration files. The vulnerability's persistence through the .vars file writing mechanism means that the attacker's modifications can survive application restarts and continue to provide access to the compromised system. This characteristic makes the vulnerability particularly dangerous in environments where bulletin board systems serve as primary communication platforms for organizations. The attack can be executed remotely without requiring prior authentication, making it an attractive target for automated exploitation tools. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence mechanisms, specifically leveraging the T1078 credential access technique and T1083 file and directory discovery to establish long-term access to the compromised system. The vulnerability also demonstrates characteristics of T1566 credential access through social engineering, as attackers may use the compromised system to gather additional information or manipulate user accounts.
Mitigation strategies for CVE-2007-3208 require immediate implementation of input validation and sanitization controls across all user-facing application interfaces. Organizations should implement strict filtering of CRLF sequences in all user inputs, particularly those processed by the register.pl and profile.pl scripts. The most effective approach involves implementing proper output encoding and input validation at multiple layers of the application architecture, including the web application firewall and application code itself. Security patches should be applied immediately to upgrade to versions of YaBB that address this vulnerability, as the original version 2.1 is no longer supported and lacks modern security controls. Network-based mitigations should include monitoring for unusual patterns of CRLF sequences in HTTP requests, particularly in parameters related to user registration and profile management. The implementation of proper logging and monitoring systems can help detect exploitation attempts and provide early warning of potential compromise. Additionally, organizations should implement principle of least privilege access controls, ensuring that the application's file writing capabilities are restricted to only necessary operations and that file permissions are properly configured to prevent unauthorized modifications. Regular security assessments and vulnerability scanning should be conducted to identify similar injection vulnerabilities in other application components, as this type of flaw often indicates broader security weaknesses in the application architecture that may affect other functionality beyond the specific vulnerable scripts.