Next.js X-Middleware Prefetch Component Cache Poisoning Scanner

Next.js is a JavaScript framework created by Vercel that enables developers to build server-rendered React applications with ease. Widely used across web development projects, it is appreciated for its feature-rich setup, which includes server-side rendering, static site generation, and a powerful routing system. From individual developers to large-scale enterprises, Next.js powers many production web platforms, giving them performance and scalability capabilities. Its versatility allows it to be integrated into existing applications or serve as the backbone of entirely new ones. Designed to enhance development efficiency, Next.js provides an optimization-rich environment for both client-side and server-side code. Its robust ecosystem and supportive community have made it a popular choice for diverse web development needs.

Cache poisoning is a vulnerability that allows attackers to manipulate web cache content by injecting malicious payloads, which can change the delivered assets to users. In Next.js, this vulnerability specifically involves exploiting the X-Middleware-Prefetch header. Attackers can poison the cache, leading to unwanted behavior on sites using Next.js, potentially damaging both user experience and site integrity. Such vulnerabilities might cause the delivery of malicious content or incorrect data potentially altering user trust in the web application. Identifying cache poisoning is crucial for maintaining the security of applications developed with Next.js and ensuring that cached data can't be compromised. This vulnerability often relies on misleading the caching mechanism into storing incorrect information, which is then indiscriminately served to unsuspecting users.

The Cache Poisoning vulnerability in Next.js involves crafting HTTP requests using the X-Middleware-Prefetch header, which can alter the server's response caching behavior. Browser or intermediary caches mistakenly regard these modified responses as legitimate, serving them to users. The specific vector involves manipulating request headers to unset specific response characteristics via the affected endpoint. Exploiting this typically requires sending multiple crafted HTTP requests to a Next.js application, using headers and priority settings that bypass intended middleware treatments. The vulnerability focuses on the ability to control or overwrite certain expected middleware responses, making poisoned content appear authentic. This allows an attacker to stage attacks where modified or harmful data can be projected onto otherwise secure applications, undermining their reliability.

Once exploited, cache poisoning can cause major disruptions in how a Next.js-based application operates and is perceived by its users. Users can be presented with incorrect or manipulated data, which might lead to security threats like cross-site scripting (XSS), phishing, or the propagation of deceptive content. These manipulations can degrade user trust and result in data integrity issues. Additionally, a successful cache poisoning attack could harm an organization's reputation and lead to potential legal and compliance ramifications. The effects also include performance degradation as malicious requests and responses become embedded in the caching strategy, presenting sustained misbehavior that confounds average debugging approaches.

REFERENCES

• https://zhero-web-sec.github.io/research-and-things/nextjs-and-cache-poisoning-a-quest-for-the-black-hole