CVE-2012-2374 in tornado
Summary
by MITRE
CRLF injection vulnerability in the tornado.web.RequestHandler.set_header function in Tornado before 2.2.1 allows remote attackers to inject arbitrary HTTP headers and conduct HTTP response splitting attacks via crafted input.
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Analysis
by VulDB Data Team • 12/02/2021
The CVE-2012-2374 vulnerability represents a critical CRLF injection flaw within the Tornado web framework's RequestHandler.set_header function, affecting versions prior to 2.2.1. This vulnerability stems from insufficient input validation and sanitization mechanisms that fail to properly escape or filter carriage return and line feed characters within HTTP header values. The issue manifests when user-supplied data containing CRLF sequences is directly incorporated into HTTP response headers without proper sanitization, creating a pathway for malicious actors to manipulate HTTP responses.
The technical exploitation of this vulnerability occurs through the manipulation of HTTP header values that are processed by the set_header function in Tornado's web framework. When an attacker crafts input containing carriage return and line feed characters, these sequences can be interpreted by the HTTP protocol parser as delimiters between different header fields or between headers and the response body. This enables attackers to inject additional HTTP headers or even append arbitrary content to the HTTP response, effectively allowing for HTTP response splitting attacks. The vulnerability is classified under CWE-117, which specifically addresses improper output neutralization for logs, and falls within the ATT&CK technique T1566 for credential access through response manipulation.
The operational impact of this vulnerability extends beyond simple header injection, as it enables sophisticated attack vectors including session hijacking, cross-site scripting, and cache poisoning. Attackers can exploit this flaw to manipulate browser behavior by injecting malicious headers that redirect users to malicious sites, inject scripts into responses, or manipulate session cookies. The vulnerability is particularly dangerous because it operates at the HTTP protocol level, making it difficult to detect through traditional application security measures and potentially allowing attackers to bypass security controls that operate at higher application layers. Response splitting attacks enabled by this vulnerability can also be used to perform cache poisoning attacks against proxy servers or content delivery networks, amplifying the attack scope and impact.
Mitigation strategies for CVE-2012-2374 require immediate patching of affected Tornado versions to 2.2.1 or later, which includes proper input validation and sanitization of header values. Organizations should implement comprehensive header sanitization routines that strip or encode CRLF characters from user-supplied input before processing. Additional defensive measures include deploying web application firewalls that can detect and block suspicious header sequences, implementing strict input validation at all application entry points, and conducting regular security assessments to identify similar vulnerabilities in custom code. The vulnerability demonstrates the critical importance of proper input sanitization in web applications and aligns with security best practices outlined in OWASP Top 10 and NIST cybersecurity frameworks. Organizations must also consider implementing automated monitoring systems that can detect anomalous HTTP header patterns indicative of potential exploitation attempts.