CVE-2014-2137 in Web Security Appliance
Summary
by MITRE
CRLF injection vulnerability in the web framework in Cisco Web Security Appliance (WSA) 7.7 and earlier allows remote attackers to inject arbitrary HTTP headers and conduct redirection attacks via a crafted URL, aka Bug ID CSCuj61002.
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Analysis
by VulDB Data Team • 05/09/2026
The Cisco Web Security Appliance WSA 7.7 and earlier versions contain a critical CRLF injection vulnerability that fundamentally compromises the integrity of HTTP header processing within the web framework. This vulnerability resides in the appliance's handling of user-supplied input in URLs, specifically allowing malicious actors to inject carriage return line feed sequences that can manipulate HTTP headers. The flaw enables attackers to insert arbitrary headers into HTTP responses, potentially bypassing security controls and redirecting users to malicious destinations. The vulnerability is particularly dangerous because it operates at the HTTP protocol level where security boundaries are typically established, making it a severe threat to web application security and network access control mechanisms. This issue represents a classic example of improper input validation where the appliance fails to properly sanitize user-provided data before incorporating it into HTTP responses.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious URL containing CRLF sequences that are not properly escaped or filtered by the WSA appliance. When the appliance processes this malformed input, it incorporates the injected sequences into HTTP headers, allowing for header injection attacks. The injected headers can contain redirection directives, authentication bypass attempts, or other malicious content that can be interpreted by web browsers or intermediate proxies. This vulnerability specifically affects the web framework component of the appliance, which is responsible for processing HTTP requests and responses, making it a core security component that directly impacts the appliance's ability to enforce security policies. The flaw is categorized under CWE-113, which describes improper neutralization of CRLF sequences in HTTP headers, and represents a direct violation of secure coding practices for input validation and output encoding.
The operational impact of this vulnerability extends beyond simple header injection, as it enables sophisticated attack vectors including open redirect attacks, session hijacking, and cache poisoning. Attackers can leverage this vulnerability to redirect users to phishing sites, inject malicious content into web applications, or bypass authentication mechanisms that rely on proper HTTP header handling. The vulnerability affects the appliance's core functionality as a web security gateway, potentially allowing attackers to circumvent the very security controls that the appliance is designed to provide. This creates a dangerous situation where the security device itself becomes a vector for attacks rather than a protective barrier. The vulnerability's impact is particularly severe in enterprise environments where the WSA appliance serves as a central point for web traffic filtering and security enforcement, potentially allowing attackers to gain unauthorized access to internal resources or exfiltrate sensitive data.
Mitigation strategies for this vulnerability require immediate patching of the affected Cisco Web Security Appliance versions to address the underlying input validation flaw. Organizations should implement network segmentation and monitoring to detect anomalous HTTP header patterns that may indicate exploitation attempts. The appliance configuration should be reviewed to ensure proper input sanitization is in place, and administrators should consider implementing additional security controls such as web application firewalls or intrusion detection systems to detect and prevent exploitation attempts. Security teams should also conduct thorough vulnerability assessments to identify any potential compromise of the appliance's security posture and ensure that all network traffic is properly monitored for signs of redirection attacks or header injection attempts. The vulnerability demonstrates the critical importance of proper input validation and output encoding in security-critical applications, aligning with ATT&CK technique T1071.004 for application layer protocol tunneling and T1566 for phishing attacks that could be facilitated through this vulnerability.