CVE-2022-24790 is a vulnerability classified under CWE-444, known as HTTP Request Smuggling, affecting the Puma HTTP server, a widely used multi-threaded, parallel HTTP 1.1 server for Ruby/Rack applications. The issue arises when Puma is deployed behind a front-end proxy that does not strictly enforce the HTTP/1.1 protocol as defined in RFC7230. Specifically, the proxy and Puma may interpret the boundaries of HTTP requests differently, leading to inconsistent parsing of the request stream. This discrepancy allows an attacker to craft specially formed HTTP requests that are 'smuggled' through the proxy and interpreted differently by Puma. Such smuggled requests can bypass security controls implemented at the proxy layer, potentially leading to unauthorized actions such as cache poisoning, request hijacking, or bypassing authentication mechanisms. The vulnerability affects Puma versions prior to 4.3.12 and versions from 5.0.0 up to but not including 5.6.4, where the issue has been addressed. No known exploits have been reported in the wild to date. Mitigation involves upgrading Puma to versions 4.3.12 or 5.6.4 and above, and configuring any front-end proxies to strictly validate incoming HTTP requests against RFC7230 to ensure consistent request parsing. This vulnerability is medium severity due to the complexity of exploitation and the requirement for a proxy misconfiguration or lax validation, but it can have significant impacts if exploited.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on Puma as their web server behind proxies such as Nginx, HAProxy, or cloud-based load balancers that may not enforce strict HTTP request validation. Exploitation could allow attackers to bypass security controls at the proxy level, leading to unauthorized access, session hijacking, or injection of malicious requests. This can compromise confidentiality by exposing sensitive data, integrity by altering request handling or injecting malicious payloads, and availability if attackers cause server misbehavior or denial of service. Organizations in sectors such as finance, healthcare, e-commerce, and government, which often deploy Ruby on Rails applications using Puma, are particularly at risk. The lack of known exploits reduces immediate risk, but the potential for targeted attacks remains, especially in environments where proxies are not properly configured. Additionally, the multi-threaded nature of Puma could exacerbate the impact by allowing concurrent exploitation attempts. Overall, the vulnerability could undermine trust in web applications and lead to regulatory and reputational damage under European data protection laws if exploited.

1. Immediate upgrade of Puma to versions 4.3.12 or 5.6.4 and later to incorporate the official patch addressing the HTTP request smuggling vulnerability. 2. Audit and harden front-end proxy configurations (e.g., Nginx, HAProxy, AWS ALB) to enforce strict compliance with RFC7230, including enabling all available request validation features such as rejecting malformed or ambiguous HTTP headers and requests. 3. Implement comprehensive logging and monitoring at both proxy and Puma server levels to detect anomalous or suspicious HTTP request patterns indicative of smuggling attempts. 4. Conduct penetration testing focused on HTTP request smuggling scenarios to validate the effectiveness of proxy and server configurations. 5. Where possible, deploy Web Application Firewalls (WAFs) with rules specifically designed to detect and block HTTP request smuggling attacks. 6. Educate development and operations teams about the risks of HTTP request smuggling and the importance of consistent HTTP parsing across the request chain. 7. Consider architectural changes to reduce reliance on proxies that do not support strict HTTP validation or to use proxies known to handle HTTP parsing robustly. These steps go beyond generic patching by emphasizing proxy configuration and detection mechanisms critical to mitigating this vulnerability effectively.