CVE-2016-1900 in CGit
Summary
by MITRE
CRLF injection vulnerability in the cgit_print_http_headers function in ui-shared.c in CGit before 0.12 allows remote attackers with permission to write to a repository to inject arbitrary HTTP headers and conduct HTTP response splitting attacks or cross-site scripting (XSS) attacks via newline characters in a filename.
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Analysis
by VulDB Data Team • 07/05/2022
The CVE-2016-1900 vulnerability represents a critical CRLF injection flaw in the CGit web interface software, specifically within the cgit_print_http_headers function located in the ui-shared.c file. This vulnerability exists in CGit versions prior to 012 and fundamentally stems from inadequate input validation of filenames before they are processed for HTTP header generation. The flaw allows authenticated attackers with write permissions to a repository to inject malicious newline characters that can manipulate HTTP response headers, creating a dangerous attack vector for various malicious activities.
The technical implementation of this vulnerability exploits the insecure handling of user-supplied data within the HTTP header construction process. When a filename containing newline characters is processed by the cgit_print_http_headers function, these characters are not properly sanitized or escaped before being incorporated into HTTP headers. This creates an opportunity for attackers to inject additional HTTP headers or manipulate existing ones, enabling sophisticated attack patterns that can bypass security controls and compromise web application integrity. The vulnerability directly maps to CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers, and aligns with ATT&CK technique T1071.004 for application layer protocol manipulation.
The operational impact of this vulnerability extends beyond simple header injection, as it enables both HTTP response splitting attacks and cross-site scripting exploitation. Attackers can leverage this vulnerability to inject malicious headers that redirect users to malicious sites, manipulate browser behavior, or inject scripts that execute in the context of other users' sessions. The HTTP response splitting aspect allows attackers to inject multiple HTTP responses, potentially enabling cache poisoning attacks or session hijacking. The XSS component provides additional attack surface where malicious scripts can be executed in victim browsers, creating persistent threats that can compromise user data and session information. The vulnerability's exploitation requires only repository write permissions, making it particularly dangerous in environments where multiple users have access to shared repositories.
Mitigation strategies for CVE-2016-1900 focus on implementing proper input validation and sanitization of filename data before HTTP header generation. Organizations should immediately upgrade to CGit version 0.12 or later, which contains the necessary patches to prevent CRLF character injection. Additional defensive measures include implementing strict input validation that removes or encodes newline characters in filenames, deploying web application firewalls that can detect and block suspicious header injection patterns, and establishing proper access controls to limit write permissions to repositories. Security monitoring should include detection of unusual HTTP header patterns and malformed requests that may indicate exploitation attempts. The vulnerability demonstrates the critical importance of sanitizing user input in web applications and aligns with security best practices outlined in OWASP Top Ten and NIST cybersecurity guidelines, particularly focusing on preventing injection flaws that can lead to session management and data integrity compromises.