Overview
The vulnerability CVE-2025-43864 affects versions 7.2.0 to 7.5.1 of React Router, a popular router used in React applications. Exploitation of this vulnerability can lead to cache poisoning, resulting in severe application disruption or even system compromise. As React Router is widely used within various web applications, the impact of this vulnerability is broad and significant.
Vulnerability Summary
CVE ID: CVE-2025-43864
Severity: High (7.5)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Successful exploitation results in application disruption due to cache poisoning, potentially leading to system compromise and data leakage.
Affected Products
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Product | Affected Versions
React Router | 7.2.0 to 7.5.1
How the Exploit Works
The exploit takes advantage of a flaw in the React Router. By adding a specific header to a request, an attacker can force the application to switch from Server-Side Rendering (SSR) to Single Page Application (SPA) mode. This causes an error that corrupts the application page. If a cache system is present, the error response can be cached, resulting in cache poisoning. This disrupts the application’s availability and can potentially lead to system compromise or data leakage.
Conceptual Example Code
Here is a conceptual example of an HTTP request that might be used to exploit this vulnerability:
GET / HTTP/1.1
Host: target.example.com
X-Force-SPA: true
This request includes the custom `X-Force-SPA` header (not a real header, used for illustrative purposes), designed to force the application into SPA mode from SSR, thereby triggering the vulnerability.
Mitigation
Users are advised to apply the vendor patch (version 7.5.2) to mitigate the vulnerability. If immediate patching is not possible, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as temporary mitigation until the patch can be applied.

