CVE-2023-30798 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) found in the Encode Starlette Python framework, specifically in versions prior to 0.25.0. The issue arises from the MultipartParser component, which processes multipart form data in HTTP requests. An unauthenticated remote attacker can exploit this flaw by crafting HTTP requests containing an excessive number of form fields or file uploads. Because the parser does not impose limits on the number of parts, this can lead to excessive memory consumption on the server. The uncontrolled resource usage can degrade performance or cause the HTTP service to crash, resulting in a denial of service (DoS). The vulnerability does not affect confidentiality or integrity but severely impacts availability. It requires no authentication or user interaction, making it straightforward to exploit remotely. The CVSS v3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) reflects a high-severity DoS vulnerability with network attack vector and low attack complexity. No known exploits have been reported in the wild as of the publication date. The recommended remediation is to upgrade Starlette to version 0.25.0 or later, where this issue is addressed. Additionally, implementing server-side limits on multipart form data size and part counts can mitigate the risk. Monitoring for abnormal multipart request patterns can help detect exploitation attempts early.

For European organizations, this vulnerability poses a significant risk to the availability of web services built on the Starlette framework. A successful attack can lead to service outages, disrupting business operations, customer access, and critical online services. This is particularly impactful for sectors relying on web applications for real-time data processing, e-commerce, or public services. The denial of service can cause reputational damage and financial losses due to downtime. Since the vulnerability is exploitable without authentication, attackers can launch large-scale or targeted DoS attacks with minimal effort. Organizations with limited incident response capabilities or those that have not updated their dependencies are at higher risk. The impact is magnified in environments where Starlette is used as a core component in microservices or API backends, common in modern European IT infrastructures. Additionally, regulatory compliance frameworks in Europe emphasize service availability, so prolonged outages could have legal and compliance repercussions.

1. Upgrade the Starlette framework to version 0.25.0 or later immediately to apply the official fix for this vulnerability. 2. Implement strict server-side limits on multipart form data processing, including maximum number of parts, maximum size per part, and total request size, to prevent resource exhaustion. 3. Employ web application firewalls (WAFs) or reverse proxies capable of detecting and blocking abnormal multipart/form-data requests with excessive parts or files. 4. Monitor HTTP request patterns for spikes in multipart form submissions or unusual request sizes that could indicate exploitation attempts. 5. Conduct regular dependency audits and vulnerability scans to ensure all components are up to date. 6. In high-risk environments, consider rate limiting or CAPTCHA challenges on endpoints accepting multipart form data to reduce automated attack feasibility. 7. Prepare incident response plans to quickly identify and mitigate DoS attacks targeting this vulnerability. 8. Educate development and operations teams about secure handling of multipart data and resource management best practices.