CVE-2016-3118 in API Gateway
Summary
by MITRE
CRLF injection vulnerability in CA API Gateway (formerly Layer7 API Gateway) 7.1 before 7.1.04, 8.0 through 8.3 before 8.3.01, and 8.4 before 8.4.01 allows remote attackers to have an unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 02/04/2019
The CVE-2016-3118 vulnerability represents a critical CRLF injection flaw within CA API Gateway, formerly known as Layer7 API Gateway, affecting multiple version ranges including 7.1 before 7.1.04, 8.0 through 8.3 before 8.3.01, and 8.4 before 8.4.01. This vulnerability resides in the gateway's handling of input validation processes where malicious actors can manipulate carriage return and line feed characters to inject malicious content into HTTP responses. The flaw stems from inadequate sanitization of user-supplied input that flows through the API gateway's processing pipeline, creating opportunities for attackers to manipulate HTTP headers and response content. The vulnerability classification aligns with CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers, making it a direct descendant of well-known HTTP header injection vulnerabilities.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input that contains CRLF sequences, typically represented as \r\n or %0d%0a, which are then processed by the API gateway without proper validation. This allows attackers to inject additional HTTP headers or manipulate existing response content, potentially enabling various attack vectors including HTTP response splitting, cache poisoning, or even session manipulation. The unspecified impact mentioned in the description suggests that the vulnerability could enable multiple attack scenarios depending on how the injected content is processed downstream by the application or network infrastructure. The attack surface is particularly concerning because API gateways serve as central points of control for API traffic, making successful exploitation potentially devastating for the entire API ecosystem.
The operational impact of this vulnerability extends beyond simple HTTP header manipulation, as it can compromise the integrity of API communications and potentially provide attackers with unauthorized access to sensitive data or services. When an API gateway is compromised through CRLF injection, attackers can manipulate authentication headers, inject malicious content into responses, or redirect traffic to malicious endpoints. The vulnerability's presence in multiple version ranges indicates a widespread exposure across the product lifecycle, suggesting that organizations may have been vulnerable for extended periods without detection. This type of vulnerability particularly affects organizations that rely heavily on API gateways for securing and managing API traffic, as the compromised gateway can become a pivot point for further attacks within the network infrastructure.
Organizations should implement immediate mitigations including input validation controls, regular security updates, and monitoring for anomalous HTTP header patterns. The vulnerability's characteristics align with ATT&CK technique T1071.004, which covers application layer protocol manipulation, and T1566, covering phishing through social engineering. Security teams should deploy web application firewalls to detect and block CRLF injection attempts, implement strict input validation policies, and ensure all API gateway instances are updated to patched versions. Additionally, network monitoring should be enhanced to detect unusual header injection patterns, and access controls should be reviewed to limit the potential impact of successful exploitation. The vulnerability demonstrates the critical importance of proper input sanitization in API gateway implementations and highlights the need for comprehensive security testing of middleware components that handle user input.