Overview
The vulnerability, CVE-2025-49826, is a notable security risk concerning Next.js, a popular React framework for web application development. The vulnerability poses a significant risk to full-stack web applications developed using affected versions of Next.js. It primarily leads to a Denial of Service (DoS) condition, potentially compromising systems or leading to data leakage.
Vulnerability Summary
CVE ID: CVE-2025-49826
Severity: High, CVSS Score: 7.5
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: DoS condition, potential system compromise and data leakage
Affected Products
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Product | Affected Versions
Next.js | 15.0.4-canary.51 to 15.1.7
How the Exploit Works
The exploit works by taking advantage of a cache poisoning bug in the Next.js framework. In certain circumstances, it allows an HTTP 204 response to be cached for static pages. This cached response can then be served to all users attempting to access the page, leading to a Denial of Service (DoS) condition as the page becomes inaccessible.
Conceptual Example Code
An attacker might exploit this vulnerability using a malformed HTTP request that triggers the HTTP 204 response. This could look something like:
GET /static_page HTTP/1.1
Host: target.example.com
Cache-Control: no-cache
Pragma: no-cache
HTTP/1.1 204 No Content
Cache-Control: max-age=86400
...The attacker sends a request to a static page, forcing a 204 No Content response which then gets cached. Future legitimate requests to the same page receive the cached 204 response, effectively making the page unavailable.
Mitigation
The issue has been addressed in version 15.1.8 of Next.js. Users of the affected versions should update to the patched version as soon as possible. As a temporary solution, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) may be used to detect and block attempts to exploit this vulnerability.
