Servify Express is a Node.js package to start an Express server and log the port its running on. Prior to 1.2, the Express server used express.json() without a size limit, which could allow attackers to send extremely large request bodies. This can cause excessive memory usage, degraded performance, or process crashes, resulting in a Denial of Service (DoS). Any application using the JSON parser without limits and exposed to untrusted clients is affected. The issue is not a flaw in Express itself, but in configuration. This issue is fixed in version 1.2. To work around, consider adding a limit option to the JSON parser, rate limiting at the application or reverse-proxy level, rejecting unusually large requests before parsing, or using a reverse proxy (such as NGINX) to enforce maximum request body sizes.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html