CVE-2025-67731 is a vulnerability categorized under CWE-400 (Uncontrolled Resource Consumption) affecting the Aarondoran servify-express Node.js package versions before 1.2. Servify-express is designed to start an Express server and log the port it runs on. The vulnerability arises because the package uses express.json() middleware without specifying a size limit on the incoming JSON request bodies. Express’s json parser, when configured without limits, will attempt to parse any size of JSON payload, which can be exploited by attackers sending very large request bodies. This leads to excessive memory allocation and CPU usage, potentially causing the Node.js process to crash or become unresponsive, resulting in a Denial of Service (DoS). The vulnerability is remotely exploitable without authentication or user interaction, making it highly accessible to attackers. The root cause is a configuration oversight rather than a flaw in Express itself. The issue was addressed in servify-express version 1.2 by introducing size limits on the JSON parser. Additional mitigations include implementing rate limiting at the application or reverse proxy level, rejecting large requests before parsing, and using reverse proxies like NGINX to enforce maximum request body sizes. No known exploits are currently reported in the wild, but the high CVSS score (8.7) reflects the potential impact and ease of exploitation. Organizations using servify-express versions prior to 1.2 in publicly accessible environments should prioritize patching or applying mitigations to prevent service disruption.

The primary impact of CVE-2025-67731 is Denial of Service (DoS) caused by uncontrolled resource consumption. For European organizations, especially those running public-facing APIs or web services using servify-express versions prior to 1.2, this vulnerability can lead to service outages, degraded performance, and increased operational costs due to resource exhaustion. This may affect customer trust, regulatory compliance (e.g., GDPR mandates on service availability), and business continuity. Critical infrastructure or services relying on Node.js and servify-express could experience downtime, impacting sectors such as finance, healthcare, and government services. The vulnerability does not directly compromise confidentiality or integrity but severely affects availability. Attackers can exploit this remotely without authentication, increasing the risk of widespread exploitation if unpatched. Organizations with high traffic volumes or limited resource capacity are particularly vulnerable. The absence of known exploits in the wild suggests a window for proactive mitigation before active attacks emerge.

1. Upgrade servify-express to version 1.2 or later, where the JSON parser size limit is enforced by default. 2. If immediate upgrade is not feasible, explicitly configure express.json() middleware with a strict size limit (e.g., limit: '100kb') to prevent excessively large payloads. 3. Implement rate limiting at the application level to restrict the number of requests per client IP, reducing the risk of resource exhaustion. 4. Deploy reverse proxies such as NGINX or HAProxy configured to reject requests exceeding a defined maximum body size, preventing large payloads from reaching the application. 5. Monitor application logs and resource usage to detect abnormal spikes in request sizes or memory consumption indicative of exploitation attempts. 6. Conduct regular security reviews of middleware configurations to ensure best practices are followed. 7. Educate development teams about secure default configurations and the risks of unbounded JSON parsing. 8. Consider deploying Web Application Firewalls (WAFs) with rules to block unusually large or malformed JSON requests. These measures collectively reduce the attack surface and improve resilience against DoS attacks exploiting this vulnerability.