CVE-2019-17513 in Ratpack
Summary
by MITRE
An issue was discovered in Ratpack before 1.7.5. Due to a misuse of the Netty library class DefaultHttpHeaders, there is no validation that headers lack HTTP control characters. Thus, if untrusted data is used to construct HTTP headers with Ratpack, HTTP Response Splitting can occur.
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Analysis
by VulDB Data Team • 01/16/2024
The vulnerability identified as CVE-2019-17513 represents a critical security flaw in the Ratpack web framework version 1.7.4 and earlier, which stems from improper handling of HTTP headers through the Netty library's DefaultHttpHeaders class. This issue creates a pathway for HTTP response splitting attacks, a well-known vulnerability pattern that has been documented under CWE-113 in the Common Weakness Enumeration catalog. The flaw occurs when applications using Ratpack process untrusted input data to construct HTTP headers without proper validation of control characters, allowing malicious actors to inject additional HTTP headers or manipulate response content.
The technical root cause of this vulnerability lies in the misimplementation of the Netty library's DefaultHttpHeaders class, which fails to validate that HTTP headers do not contain HTTP control characters such as carriage return and line feed characters. These control characters, when present in HTTP headers, can be exploited to inject additional headers or manipulate the HTTP response structure. The vulnerability specifically affects the header construction process within Ratpack applications, where user-supplied data is directly incorporated into HTTP headers without proper sanitization or validation. This pattern of improper input handling creates a direct pathway for attackers to inject malicious headers that can be interpreted by HTTP clients as separate responses, leading to response splitting.
The operational impact of this vulnerability extends beyond simple header injection, as HTTP response splitting can enable various attack vectors including cross-site scripting attacks, cache poisoning, and session hijacking. When an attacker successfully exploits this vulnerability, they can inject additional HTTP headers that may cause web browsers to interpret the response incorrectly, potentially leading to the execution of malicious code in the context of the victim's browser. This vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1190 category for exploitation of remote services, specifically targeting the manipulation of HTTP responses to achieve unauthorized access or data manipulation. The attack surface is particularly concerning for web applications that accept user input for header construction, as the vulnerability can be exploited even with minimal privileges.
Mitigation strategies for CVE-2019-17513 primarily focus on upgrading to Ratpack version 1.7.5 or later, where the vulnerability has been addressed through proper header validation. Organizations should also implement input sanitization measures that validate all user-supplied data before incorporating it into HTTP headers, ensuring that control characters are properly escaped or removed. Additionally, security teams should conduct comprehensive code reviews to identify other potential instances of similar vulnerabilities within their applications, particularly focusing on any direct usage of Netty's DefaultHttpHeaders or similar classes. Network security controls including web application firewalls and HTTP header validation rules can provide additional defense-in-depth measures, while monitoring systems should be configured to detect unusual header patterns that may indicate exploitation attempts. The remediation process should also include thorough testing to ensure that the upgrade does not introduce compatibility issues with existing application functionality, and security teams should verify that all applications using Ratpack have been properly updated to prevent exploitation of this vulnerability.