CVE-2025-32907 is an important security vulnerability that affects the libsoup library which is widely used in various applications to handle HTTP communications. In this post, we will examine the details of this vulnerability, as well as how it can be exploited in a resource consumption attack. Furthermore, there will be an analysis of a code snippet and links to original references to help you better understand the issue at hand. Finally, we will present tips to mitigate this vulnerability. Keep reading to learn more about this flaw and how you can protect your applications from being exploited.

Background

Libsoup is an HTTP client/server library for GNOME, designed to support high-level features like cookies, authentication, proxy support, and more. It is built on top of the Glib Object System and provides a simple, efficient, and flexible way to handle HTTP communications for any GNOME-based application. However, as with any software, it may contain vulnerabilities that can be exploited by malicious actors.

The vulnerability (CVE-2025-32907)

A flaw was discovered in the libsoup library regarding the implementation of HTTP range requests. Range requests are a feature introduced in HTTP/1.1 that allows clients to request only a specific range of a document, rather than the whole file. This is particularly useful for partial downloads, seeking within a large video or audio file, and resuming interrupted downloads.

The vulnerability in libsoup's implementation of range requests lies within the way it processes multiple ranges in the same request. As per the HTTP/1.1 specification, a client can request multiple byte ranges in a single request by specifying them in a comma-separated list in the "Range" header.

For example, the following request asks for the first 100 bytes and 200 to 300 bytes of a file

GET /file.txt HTTP/1.1
Host: example.com
Range: bytes=-99,200-300

However, a malicious client can exploit this feature by requesting the same range multiple times, causing the server to generate a response for each instance of the requested range. This can lead to the server consuming significant amounts of memory and CPU resources while processing this particular request.

Exploiting the vulnerability

The following code snippet demonstrates how a malicious client could craft a request payload that exploits the vulnerability:

import requests

url = 'http://example.com/file.txt';
num_ranges = 100
range_values = 'bytes=' + ','.join(['-99'] * num_ranges)
headers = {'Range': range_values}

response = requests.get(url, headers=headers)

In the code snippet above, the malicious client requests the same byte range (-99) 100 times in a single HTTP request. This would cause the libsoup server to process every requested range and potentially consume large amounts of memory and CPU in the process.

To put the scale of this vulnerability into perspective, a document that highlights the issue can be found at CVE's website (https://example.com/CVE-2025-32907). This document details the vulnerability's impact and various associated risks.

Mitigating the vulnerability

To mitigate this vulnerability and protect your applications from being exploited, consider implementing the following best practices:

1. Update: Make sure to update the libsoup library to the latest version, which includes patches for this vulnerability.
2. Limit the number of requested ranges: Implement server-side controls to limit the number of byte ranges a client can request in a single request. This will help prevent excessive resource consumption.
3. Monitor: Continuously monitor and analyze your server logs to identify any unusual or potentially malicious activity. Early detection can help prevent an attacker from successfully exploiting your server resources.

Conclusion

CVE-2025-32907 is a significant security vulnerability that affects the libsoup library's handling of HTTP range requests. By understanding the details of this vulnerability and following the recommended best practices for mitigation, you can protect your applications from potential exploits. Stay informed about the latest security vulnerabilities and patches by regularly visiting trusted resources like the CVE website and subscribing to security mailing lists.

Timeline

Published on: 04/14/2025 14:15:24 UTC
Last modified on: 05/05/2025 03:15:22 UTC