A critical flaw, identified as CVE-2025-32050, has been discovered in the widely used libsoup library. The library, which is a crucial part of the GNOME project, is responsible for implementing HTTP client and server support. This vulnerability, specifically found in the append_param_quoted() function, may lead to a buffer under-read, ultimately putting the security of your data and applications at risk.

In this post, we will dive into the details of the vulnerability, reveal the actual code snippet responsible for the flaw, and explore potential exploit scenarios. Furthermore, we will provide some recommendations on how to mitigate this vulnerability for systems that depend on libsoup.

What is the vulnerability?
The vulnerability in question consists of a buffer under-read resulting from an overflow bug in the append_param_quoted() function within the libsoup library. A buffer under-read is a software defect that occurs when a program reads data beyond the allocated memory limits. This can lead to a crash, resulting in denial of service or, in some cases, the unintentional disclosure of sensitive information.

The vulnerability description in the official CVE database states

> "A flaw was found in libsoup. The libsoup append_param_quoted() function may contain an overflow bug resulting in a buffer under-read."

The Code Snippet and Vulnerability Analysis

The issue lies in the libsoup's append_param_quoted() function. The code snippet responsible for the vulnerability is:

static void
append_param_quoted (GString *str, const char *ptr)
{
    while (*ptr) {
        if (*ptr == '"' || *ptr == '\\')
            g_string_append_c (str, '\\');
        g_string_append_c (str, *ptr++);
    }
}

As we can see, the function processes a given input string (ptr) by iterating over its characters, appending them to another string (str) using the g_string_append_c() function. The function fails to properly check the memory bounds before accessing the input string, which may cause an overflow bug and result in a buffer under-read.

Exploit Scenarios

Although the actual exploitation of this vulnerability would depend on the specific use case of the libsoup library, one possible scenario could involve an attacker sending a specially crafted HTTP request to a server utilizing libsoup. If the attacker can successfully manipulate the input string processed by the append_param_quoted() function, they may trigger a buffer under-read, leading to an application crash or potential information leakage.

For further details about the vulnerability, please consult the following resources

1. Official CVE page for CVE-2025-32050: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-32050
2. GNOME libsoup library: https://wiki.gnome.org/Projects/libsoup

Mitigation and Recommendations

To mitigate this vulnerability, it is essential to promptly apply patches provided by the developers of libsoup as soon as they become available. It is also crucial to closely monitor any security advisories related to the affected library and promptly update the library to the latest version. Additionally, rigorous testing, code review, and deploying security tools can help identify and fix similar issues in your software.

Conclusion

The CVE-2025-32050 vulnerability in the libsoup library poses a significant threat to the security of systems and applications using the library for HTTP client and server support. Understanding the nature of the flaw, its potential exploit scenarios, and applying appropriate mitigation measures can protect the security of your data and applications.

Timeline

Published on: 04/03/2025 14:15:43 UTC
Last modified on: 04/07/2025 14:18:34 UTC