CVE-2016-1000111 in Twisted
Summary
by MITRE
Twisted before 16.3.1 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does not protect CGI applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect a CGI application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2016-1000111 affects the Twisted networking framework version 16.3.1 and earlier, representing a critical security flaw that stems from inadequate handling of RFC 3875 section 4.1.18 namespace conflicts. This issue specifically impacts CGI applications that rely on the HTTP_PROXY environment variable for outbound HTTP traffic routing. The flaw originates from the framework's failure to properly sanitize or validate client-provided proxy headers, creating an environment where malicious actors can manipulate the application's network behavior through crafted HTTP requests. This vulnerability falls under the category of insecure direct object reference and environment variable manipulation, with implications for application security and network traffic integrity.
The technical implementation of this vulnerability occurs when Twisted processes HTTP requests containing Proxy headers without properly isolating or sanitizing the HTTP_PROXY environment variable. When a CGI application running on a vulnerable Twisted framework accesses outbound HTTP connections, it inadvertently uses the proxy server specified in the client-controlled HTTP_PROXY environment variable. This creates a scenario where an attacker can inject a malicious proxy server address through a carefully crafted Proxy header in the HTTP request, effectively redirecting all outbound traffic from the CGI application through their controlled proxy server. The flaw is particularly dangerous because it operates at the framework level, affecting all CGI applications that utilize Twisted's HTTP processing capabilities.
The operational impact of this vulnerability extends beyond simple traffic redirection, as it enables sophisticated attack vectors including man-in-the-middle scenarios, data exfiltration, and network reconnaissance activities. An attacker can leverage this vulnerability to intercept sensitive data flowing from CGI applications, potentially accessing authentication tokens, session cookies, or other confidential information. The httpoxy attack pattern allows for persistent network monitoring and can be combined with other techniques to establish persistent access to target systems. This vulnerability directly impacts the confidentiality and integrity of network communications, as outlined in the CWE-200 category for exposure of sensitive information and the CWE-284 category for improper access control.
Mitigation strategies for this vulnerability require immediate patching of Twisted to version 16.3.1 or later, where the framework properly addresses the RFC 3875 namespace conflicts. Organizations should also implement network-level controls to monitor and restrict outbound HTTP traffic from CGI applications, particularly those running on vulnerable systems. Additionally, application-level protections such as environment variable sanitization and explicit proxy configuration controls should be implemented to prevent the injection of untrusted proxy server addresses. Security teams should conduct comprehensive vulnerability assessments to identify all systems running vulnerable versions of Twisted and ensure proper network segmentation to limit the potential impact of successful exploitation. The remediation process should align with the ATT&CK framework's mitigation strategies for command and control communications, specifically targeting the T1071.004 technique related to application layer protocol usage and the T1566 technique for credential access through network manipulation.