CVE-2020-1695 in RESTEasy
Summary
by MITRE
A flaw was found in all resteasy 3.x.x versions prior to 3.12.0.Final and all resteasy 4.x.x versions prior to 4.6.0.Final, where an improper input validation results in returning an illegal header that integrates into the server's response. This flaw may result in an injection, which leads to unexpected behavior when the HTTP response is constructed.
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Analysis
by VulDB Data Team • 03/14/2025
The vulnerability identified as CVE-2020-1695 represents a critical input validation flaw within the RestEasy framework, a popular Java-based RESTful web services implementation. This issue affects versions 3.x.x prior to 3.12.0.Final and 4.x.x prior to 4.6.0.Final, making it a widespread concern across multiple major releases of the framework. The flaw stems from inadequate validation of user-supplied input during HTTP response construction, creating a pathway for malicious actors to inject unauthorized headers into server responses. The vulnerability manifests when the framework fails to properly sanitize or validate input parameters that are subsequently used to construct HTTP response headers, leading to the inclusion of malformed or unexpected header values in the final response payload.
The technical nature of this vulnerability aligns with CWE-20, which describes improper input validation, and can be categorized under the broader class of injection flaws that affect web application security. When RestEasy processes incoming requests and constructs responses, it processes user-provided data through various internal mechanisms that eventually influence header generation. The improper validation allows attackers to manipulate input values in such a way that the resulting HTTP headers contain unexpected or malicious content. This can occur through parameter manipulation, header injection techniques, or other methods that bypass normal input sanitization processes. The vulnerability specifically impacts the HTTP response construction phase, where the framework's internal header handling logic fails to adequately filter or validate input that flows into header generation.
The operational impact of CVE-2020-1695 extends beyond simple header injection, potentially enabling a range of malicious activities that can compromise server integrity and application security. When illegal headers are integrated into server responses, attackers can exploit this behavior to perform various attacks including cache poisoning, cross-site scripting attempts, or server-side request forgery. The unexpected behavior resulting from malformed headers can cause downstream applications or proxies to misinterpret the response, potentially leading to security bypasses or information disclosure. Additionally, the vulnerability may enable attackers to manipulate how HTTP responses are handled by browsers, load balancers, or other intermediaries in the request-response chain. The impact is particularly concerning in environments where RestEasy serves as a core component of enterprise web applications or microservices architectures.
Mitigation strategies for CVE-2020-1695 should prioritize immediate version upgrades to the patched releases of RestEasy 3.12.0.Final or 4.6.0.Final, as these versions contain the necessary fixes to address the input validation deficiencies. Organizations should conduct thorough vulnerability assessments to identify all systems running affected RestEasy versions and implement patch management procedures to ensure timely remediation. Additional defensive measures include implementing input sanitization at multiple layers, including application-level validation of HTTP headers, network-level filtering of suspicious header content, and comprehensive monitoring of HTTP response headers for anomalous patterns. The implementation of proper header validation frameworks and adherence to secure coding practices can help prevent similar vulnerabilities from emerging in other components of the application stack. Organizations should also consider implementing security controls that detect and prevent header injection attempts, particularly in environments where RestEasy applications interact with external systems or handle sensitive user data. This vulnerability demonstrates the critical importance of maintaining up-to-date dependencies and implementing robust input validation mechanisms across all application components to prevent injection-based attacks.