CVE-2023-47627: AIOHTTP HTTP Parser Vulnerability

Background

AIOHTTP is a Python library that provides an asynchronous HTTP client and server implementation. It is widely used for building web applications and APIs. The library allows developers to handle HTTP requests and responses efficiently. However, a vulnerability has been discovered in the HTTP parser of AIOHTTP, which can lead to request smuggling attacks.

Vulnerability Detail

The vulnerability in AIOHTTP's HTTP parser has several issues related to header parsing. These issues can be exploited to perform request smuggling attacks. The specific problems include:

1. Bad parsing of Content-Length values: AIOHTTP does not enforce the correct format for Content-Length values, leading to misinterpretation.

2. Improper handling of NUL, CR, and LF characters in header values: AIOHTTP does not replace these forbidden characters with spaces, allowing them to be processed.

3. Improper stripping of whitespace before colon in HTTP headers: AIOHTTP does not enforce the rule that no whitespace should be present before the colon in header fields.

These vulnerabilities can be used by attackers to manipulate HTTP requests and potentially bypass security measures.

pip install --upgrade "aiohttp==3.14.5"

pip install --upgrade "aiohttp==3.8.6"

Workaround

If updating AIOHTTP is not immediately possible, a workaround is to manually enforce the correct format for Content-Length values, replace forbidden characters with spaces in header values, and reject messages with whitespace before the colon in header fields. Here is an example code snippet for enforcing the Content-Length format:

import aiohttp

def enforce_content_length_format(request):
    content_length = request.headers.get('Content-Length')
    if content_length and not content_length.isdigit():
        raise ValueError('Invalid Content-Length format')

# Usage:
request = aiohttp.Request()
enforce_content_length_format(request)

Please note that this is a temporary workaround and updating to the latest version of AIOHTTP is still recommended.

Conclusion

The AIOHTTP HTTP parser vulnerability exposes applications using AIOHTTP to potential request smuggling attacks. It is crucial to update AIOHTTP to version 3.8.6 or later to mitigate these vulnerabilities. If immediate updating is not possible, developers should apply the provided workaround and ensure they are enforcing the correct format for Content-Length values, replacing forbidden characters with spaces, and rejecting messages with whitespace before the colon in header fields. For further assistance and support in vulnerability remediation, please contact DevNack.com.

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