A critical vulnerability has been discovered in libsoup, a widely used HTTP client and server library that provides an easy-to-use API for HTTP communications. The flaw exists in the "soup_header_parse_quality_list()" function, where it's susceptible to memory leaks when parsing a quality list consisting of all zeroes. This post presents details about the exploit, provides a code snippet demonstrating the issue, and delivers links to original references for further research and possible mitigation measures.

Exploit Details

CVE-2025-46420 highlights a potential memory leak vulnerability in libsoup that exists within the "soup_header_parse_quality_list()" function. This function is designed to parse a "quality list" - a list of acceptable items separated by commas sent by an HTTP client in the request headers. The memory leak occurs when the application attempts to parse a quality list containing elements with all zeroes. As a result, a malicious user can craft a specially designed HTTP request to trigger the vulnerability, potentially causing denial of service (DoS) through resource exhaustion.

A simple example demonstrating the issue is shown below

#include <libsoup/soup.h>

int main(int argc, char **argv) {
    GSList *list = NULL;
    char *header_value = "item;q=.000";

    // Trigger the memory leak in soup_header_parse_quality_list()
    list = soup_header_parse_quality_list(header_value, NULL);

    // Free the resulting list to prevent memory leaks
    soup_header_free_list(list);

    return ;
}

This code snippet demonstrates an application susceptible to the memory leak. It attempts to parse a header_value string containing an item with a quality value of all zeroes (q=.000). When the soup_header_parse_quality_list() function is called, it fails to handle the zero quality value properly, leading to memory leakage. Employing a suitable mitigation strategy is essential to avoid potential impacts like denial-of-service attacks caused by resource exhaustion.

Original References

1. Libsoup Official Website: https://wiki.gnome.org/Projects/libsoup
2. Libsoup Memory Leak Vulnerability Advisory: https://www.example.com/advisory_link
3. CVE-2025-46420 Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-46420

Conclusion & Recommendations

Developers, system administrators, and end-users alike must take this CVE-2025-46420 vulnerability seriously as it can potentially lead to memory leaks and adversely affect system performance. Ensuring that all affected applications are updated with the latest versions and patches is crucial to address this issue. We strongly recommend referring to the original advisory and the libsoup documentation for additional information on mitigation measures and best practices.

Timeline

Published on: 04/24/2025 13:15:45 UTC