CVE-2025-48075 is a high-severity vulnerability affecting the Fiber web framework, a popular Express-inspired framework written in Go. The issue exists in versions 2.52.6 and prior to 2.52.7 within the `fiber.Ctx.BodyParser` function, which is responsible for parsing HTTP request bodies. This function supports mapping flat data to nested slices using a syntax like `key[idx]value`. However, when the index `idx` is negative, the function does not properly validate the array index and instead of returning an error, it causes a panic. This improper validation of array indices corresponds to CWE-129. Since the data parsed is user-controlled, an attacker can craft malicious requests with negative indices to trigger this panic, causing the Fiber application to crash or become unavailable. This results in a denial of service (DoS) condition for any service relying on this parsing functionality. The vulnerability does not require authentication, user interaction, or privileges, and can be exploited remotely over the network. The issue was fixed in version 2.52.7 by adding proper validation to reject negative indices gracefully. The CVSS 4.0 base score is 7.7, reflecting high severity due to the ease of exploitation and the impact on availability. No known exploits are reported in the wild yet, but the simplicity of triggering the panic makes it a significant risk for affected deployments.

For European organizations using the Fiber framework in web applications or APIs, this vulnerability poses a risk of service disruption through denial of service attacks. Attackers can remotely send specially crafted HTTP requests that cause the application to panic and crash, leading to downtime and potential loss of availability for end users. This can affect critical business services, customer-facing portals, or internal APIs, impacting operational continuity and user trust. Organizations in sectors such as finance, healthcare, e-commerce, and government, which often rely on web frameworks for their digital services, may experience significant disruption. Additionally, repeated exploitation attempts could increase operational costs due to incident response and recovery efforts. While the vulnerability does not directly expose sensitive data or allow code execution, the loss of availability can indirectly affect confidentiality and integrity if fallback mechanisms or error handling are inadequate. The impact is particularly relevant for high-availability environments and services with strict uptime requirements.

European organizations should immediately assess their use of the Fiber framework, specifically checking if versions between 2.52.6 and prior to 2.52.7 are in use. The primary mitigation is to upgrade Fiber to version 2.52.7 or later, where the vulnerability is fixed. If immediate upgrading is not feasible, organizations should implement input validation at the application or web server level to reject HTTP requests containing suspicious or malformed keys with negative indices before they reach the Fiber parser. Additionally, deploying Web Application Firewalls (WAFs) with custom rules to detect and block such malformed requests can reduce exposure. Monitoring application logs for panic events or crashes related to `BodyParser` can help detect exploitation attempts early. Implementing robust error handling and graceful degradation in the application can minimize downtime in case of unexpected input. Finally, organizations should review their incident response plans to include scenarios involving DoS via malformed HTTP requests and ensure rapid patch deployment processes are in place.