CVE-2019-11284 in Pivotal Reactor Netty
Summary
by MITRE
Pivotal Reactor Netty, versions prior to 0.8.11, passes headers through redirects, including authorization ones. A remote unauthenticated malicious user may gain access to credentials for a different server than they have access to.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 01/16/2024
The vulnerability identified as CVE-2019-11284 affects Pivotal Reactor Netty versions prior to 0.8.11, presenting a critical security flaw in HTTP redirect handling mechanisms. This issue stems from the improper management of HTTP headers during redirect operations, specifically allowing sensitive authentication headers to be transmitted across different server boundaries. The flaw creates an unintended information disclosure channel that can be exploited by remote attackers without requiring authentication to the target system. The vulnerability manifests when the Netty HTTP client follows redirects and blindly forwards all headers from the original request to the redirected endpoint, including authorization tokens and credentials that should remain scoped to the initial server context.
The technical implementation of this vulnerability resides in the HTTP client's redirect processing logic within the Reactor Netty framework. When an HTTP request receives a redirect response, the system typically handles the transition by creating a new request to the redirected URL. However, in affected versions, the implementation fails to properly sanitize or filter headers before forwarding them to the new endpoint. This behavior violates fundamental security principles of least privilege and scope isolation, as authentication credentials that were intended for a specific server are inadvertently shared with potentially different servers. The flaw represents a classic case of improper header handling that can lead to credential leakage and unauthorized access to resources.
The operational impact of this vulnerability extends beyond simple credential disclosure, as it can enable attackers to escalate privileges and access systems they would normally be unable to reach. An attacker who can manipulate or intercept HTTP redirects can potentially use this vulnerability to gain access to services protected by authentication mechanisms that are not intended for their access. This includes scenarios where the original request contains authorization headers for one service but the redirect points to another service where those same credentials might be valid. The vulnerability particularly affects applications that rely on Netty's HTTP client for making outbound requests and that do not implement additional header sanitization measures.
Security professionals should consider this vulnerability in the context of the CWE-200 weakness classification, which covers "Information Exposure" and specifically addresses scenarios where sensitive information is inadvertently exposed through improper handling of data flows. The ATT&CK framework would categorize this as a technique involving "T1071.004 - Application Layer Protocol: DNS" and "T1566 - Phishing" in the context of credential harvesting, as attackers could leverage this flaw to obtain authentication tokens from one service and use them against another. Organizations using affected versions of Reactor Netty should prioritize immediate patching to 0.8.11 or later, as the vulnerability allows for unauthorized access without requiring authentication to the target system. Additional mitigations include implementing proper header filtering at the application level, monitoring for unusual redirect patterns, and ensuring that sensitive headers are not transmitted across server boundaries during HTTP operations.
The vulnerability highlights the importance of secure coding practices in HTTP client implementations and demonstrates how seemingly minor flaws in redirect handling can create significant security risks. Organizations should conduct thorough security reviews of their HTTP client configurations and ensure that all components properly handle header forwarding during redirect operations. The fix implemented in version 0.8.11 addresses the core issue by ensuring that authentication headers are properly filtered or stripped during redirect processing, preventing the unintended disclosure of credentials across different server contexts. This vulnerability serves as a reminder of the critical need for proper input validation and header sanitization in network communication libraries, particularly those handling authentication-sensitive data flows.