CVE-2016-1899 in CGit
Summary
by MITRE
CRLF injection vulnerability in the ui-blob handler in CGit before 0.12 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks or cross-site scripting (XSS) attacks via CRLF sequences in the mimetype parameter, as demonstrated by a request to blob/cgit.c.
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Analysis
by VulDB Data Team • 07/05/2022
The CVE-2016-1899 vulnerability represents a critical CRLF injection flaw in the ui-blob handler component of CGit versions prior to 0.12. This vulnerability falls under the CWE-113 category for Improper Neutralization of CRLF Sequences in HTTP Headers, making it a prime example of HTTP response splitting and cross-site scripting vector. The vulnerability specifically affects the blob handler functionality within the CGit web interface, which is commonly used for displaying source code files and binary content within version control systems. Attackers can exploit this weakness by manipulating the mimetype parameter through carefully crafted CRLF sequences that are not properly sanitized or validated before being processed in HTTP response headers.
The technical exploitation of this vulnerability occurs when a remote attacker sends a malicious request to the blob endpoint with a specially crafted mimetype parameter containing CRLF characters. These sequences, typically represented as \r\n or %0D%0A, are interpreted by the web server and injected into HTTP response headers, allowing attackers to manipulate the HTTP response structure. This injection capability enables attackers to perform HTTP response splitting attacks where they can inject additional HTTP headers or even multiple HTTP responses within a single request. The vulnerability is particularly dangerous because it allows for both HTTP header injection and cross-site scripting exploitation, creating multiple attack vectors within a single flaw. When combined with other vulnerabilities or used in conjunction with web application security misconfigurations, this vulnerability can lead to session hijacking, cache poisoning, or more sophisticated attack chains.
The operational impact of CVE-2016-1899 extends beyond simple header injection, as it can enable attackers to manipulate web application behavior in significant ways. In the context of CGit, which is widely used in corporate and open-source environments for code repository browsing, this vulnerability could allow attackers to inject malicious content into web responses, potentially leading to user data compromise or unauthorized access to sensitive repository information. The vulnerability affects organizations using CGit as their web interface for Git repositories, particularly those with public or semi-public repositories where unauthenticated users can access the blob handler. Security professionals should note that this vulnerability aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS, as the manipulation of HTTP headers can be used to redirect or manipulate client-side behavior. The vulnerability demonstrates the importance of proper input validation and output encoding in web applications, particularly when handling user-supplied parameters that are later used in HTTP response construction.
Organizations affected by CVE-2016-1899 should immediately implement mitigations including upgrading to CGit version 0.12 or later, which contains the necessary patches to prevent CRLF injection in the ui-blob handler. Additionally, implementing proper input sanitization and validation for all user-supplied parameters, particularly those used in HTTP header construction, can provide defense-in-depth protection. Web application firewalls should be configured to detect and block CRLF sequences in request parameters, and security headers such as Content Security Policy should be implemented to mitigate potential XSS exploitation. The vulnerability serves as a reminder of the critical importance of input validation and output encoding practices, particularly in web applications that handle user-supplied data in contexts where that data may be used to construct HTTP responses. Regular security assessments and code reviews focusing on HTTP header manipulation and input validation practices are essential for preventing similar vulnerabilities in other applications. Organizations should also consider implementing automated vulnerability scanning tools that can detect such CRLF injection patterns in their web applications, as this type of vulnerability often goes undetected during routine security testing if proper attention is not paid to HTTP response construction and parameter handling.