CVE-2022-45442 is a medium-severity vulnerability affecting the Sinatra web application framework for Ruby, specifically versions 2.0 up to but not including 2.2.3, and versions 3.0 up to but not including 3.0.4. Sinatra is widely used for building lightweight web applications and APIs in Ruby. The vulnerability arises from improper handling of the Content-Disposition HTTP header when the filename parameter is derived directly from user-supplied input without adequate validation or sanitization. This flaw enables a reflected file download (RFD) attack, where an attacker can craft a malicious URL or request that causes the server to respond with a file download prompt containing attacker-controlled content or filename. The core issue is categorized under CWE-494, which involves downloading code or content without verifying its integrity, potentially leading to users inadvertently downloading malicious files. Although no known exploits have been reported in the wild, the vulnerability can be exploited by an attacker who can induce a victim to click a specially crafted link or visit a malicious page that triggers the vulnerable Sinatra application to respond with a manipulated Content-Disposition header. This can facilitate social engineering attacks, phishing, or delivery of malicious payloads under the guise of legitimate downloads. The vulnerability does not require authentication but does require user interaction (clicking a link or visiting a URL). The patched versions 2.2.3 and 3.0.4 address this issue by properly sanitizing or restricting the filename parameter in the Content-Disposition header to prevent injection of malicious content or unintended file downloads. Organizations running vulnerable versions of Sinatra in their web applications are at risk of this reflected file download attack vector if they incorporate user input directly into response headers without validation.

For European organizations, the impact of CVE-2022-45442 primarily concerns the confidentiality and integrity of end-user interactions rather than direct compromise of backend systems. Attackers can exploit this vulnerability to trick users into downloading malicious files that appear to originate from trusted web applications, potentially leading to malware infections, credential theft, or further social engineering attacks. This can damage organizational reputation, lead to data breaches if users are compromised, and increase the risk of lateral attacks within corporate networks. Since Sinatra is popular among startups, SMEs, and some enterprise Ruby-based web services, organizations relying on these applications for customer-facing portals, APIs, or internal tools may be exposed. The vulnerability does not directly affect system availability or backend integrity but can be a stepping stone for more complex attacks targeting users. The lack of known exploits reduces immediate risk, but the ease of crafting malicious links and the widespread use of Sinatra in Europe means the threat should not be underestimated. Compliance with GDPR and other data protection regulations may be impacted if user data is compromised following exploitation. The threat is more significant for sectors with high user interaction such as e-commerce, financial services, and public sector digital services.

1. Upgrade all Sinatra applications to version 2.2.3 or 3.0.4 or later, where the vulnerability is patched. 2. Implement strict input validation and sanitization on any user-supplied data used in HTTP headers, especially Content-Disposition filenames. Avoid directly reflecting user input in response headers. 3. Employ Content Security Policy (CSP) headers to reduce the risk of malicious script execution resulting from social engineering attacks. 4. Educate end-users and employees about the risks of clicking unsolicited or suspicious download links, particularly those originating from internal or trusted web applications. 5. Monitor web application logs for unusual requests that include suspicious filename parameters in URLs or headers. 6. Use Web Application Firewalls (WAFs) with rules designed to detect and block reflected file download attempts or suspicious Content-Disposition header manipulations. 7. Conduct regular security code reviews and penetration testing focusing on header injection and reflected content vulnerabilities. 8. For applications that cannot be immediately upgraded, implement server-side filtering or middleware to sanitize or reject unsafe Content-Disposition header values derived from user input.