CVE-2012-2943 in cryptographp
Summary
by MITRE
CRLF injection vulnerability in cryptographp.inc.php in Cryptographp allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via the cfg parameter.
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Analysis
by VulDB Data Team • 03/16/2019
The CVE-2012-2943 vulnerability represents a critical CRLF injection flaw in the cryptographp.inc.php component of the Cryptographp library, a widely used PHP-based CAPTCHA implementation. This vulnerability resides in the handling of the cfg parameter within the cryptographic CAPTCHA generation process, creating a pathway for remote attackers to manipulate HTTP headers through carefully crafted input sequences. The flaw specifically enables attackers to inject carriage return line feed sequences that can disrupt normal HTTP communication protocols and manipulate response headers. The vulnerability demonstrates a classic lack of proper input validation and sanitization, where user-supplied parameters are directly incorporated into HTTP response construction without adequate filtering or encoding mechanisms.
The technical exploitation of this vulnerability occurs when an attacker provides malicious input through the cfg parameter that contains CRLF sequences such as \r\n or %0d%0a. These sequences allow the attacker to inject arbitrary HTTP headers into the response, potentially enabling HTTP response splitting attacks that can lead to various security consequences including session hijacking, cross-site scripting, and cache poisoning. The vulnerability operates at the application layer and specifically targets the HTTP protocol implementation within the PHP environment, making it particularly dangerous in web applications that rely on proper header management for security controls. This flaw aligns with CWE-113, which describes improper neutralization of CRLF sequences in HTTP headers, and represents a fundamental failure in input sanitization practices that violates established secure coding principles.
The operational impact of CVE-2012-2943 extends beyond simple header injection, as it can facilitate more sophisticated attacks that leverage HTTP response manipulation. Attackers can use this vulnerability to redirect users to malicious sites, inject malicious content into web pages, or manipulate browser behavior through crafted HTTP responses. The vulnerability is particularly concerning because it affects a component commonly used in web applications for authentication and access control, potentially allowing attackers to bypass security measures that depend on proper HTTP response handling. The exploitability of this vulnerability is high due to the widespread use of the Cryptographp library and the relatively simple nature of the attack vector that requires only parameter manipulation to achieve header injection. This vulnerability can be mapped to ATT&CK technique T1190, which covers the use of CRLF injection for HTTP response splitting, and demonstrates how basic input validation failures can lead to complex security compromise scenarios.
Mitigation strategies for CVE-2012-2943 require immediate implementation of proper input validation and sanitization measures within the affected application code. Organizations should ensure that all user-supplied input, particularly parameters used in HTTP header construction, undergoes rigorous sanitization to remove or encode CRLF sequences before processing. The recommended approach involves implementing strict input validation that rejects or filters out any sequences that could be used for header injection attacks, including both literal CRLF characters and their URL-encoded equivalents. Additionally, developers should consider implementing proper output encoding for HTTP headers and avoid direct concatenation of user input into HTTP response construction. The vulnerability highlights the importance of following secure coding practices as outlined in OWASP Top Ten and ISO/IEC 27001 security standards, particularly in the areas of input validation and output encoding. Regular security assessments and code reviews should be conducted to identify similar vulnerabilities in other components and ensure that all HTTP response handling mechanisms properly sanitize input data to prevent header injection attacks.