A flaw was recently discovered in libsoup - an HTTP client and server library for GNOME. The vulnerable function is soup_message_headers_get_content_disposition(), where a NULL pointer dereference can potentially cause a client or server using this function to crash. An attacker, that is a malicious HTTP peer, can exploit this vulnerability and cause significant disruptions to the victim's services. In this post, we will dive deeper into the details surrounding CVE-2025-32913 and explore possible ways to mitigate this issue.

Vulnerability Details

The vulnerability in question is specifically with the soup_message_headers_get_content_disposition() function in libsoup. This function is used to parse the content disposition header in an HTTP response. A NULL pointer dereference vulnerability occurs when the program attempts to access memory location zero, which is explicitly reserved by the operating system.

In this case, the NULL pointer dereference comes into play when the function encounters a malformed content disposition header that does not include a parameter. As a result, the function attempts to access a NULL pointer while parsing the header's fields.

Here's a code snippet showcasing the vulnerable function

const char *
soup_message_headers_get_content_disposition (SoupMessageHeaders *hdrs,
                                              char              **disposition_params)
{
    const char *header, *semi, *start, *end;

    header = soup_message_headers_get_list (hdrs, "Content-Disposition");
    if (!header)
        return NULL;

    end = strchr (header, ';');
    if (end) {
        while (1) {
            semi = end + 1;
            start = strchr (semi, '=');
            if (!start)
                break;

            end = strchr (start + 1, ';');
            if (!end)
                break;

            /* Vulnerable code subset here */
        }
    }

    return g_strndup (header, end - header);
}

The vulnerability is present in the while loop where no validation checks are being performed for the value of start before dereferencing it.

Exploitation

Exploiting this vulnerability is straightforward for an attacker acting as a malicious HTTP peer. The attacker can send a specially crafted HTTP response containing a malformed content disposition header, which is likely to crash the client or server relying on libsoup and this function. This can lead to denial of service (DoS) attacks, rendering the targeted services unavailable for legitimate users.

Mitigations and Patches

To protect your applications from this vulnerability, you should apply the latest patches and updates provided by the developers of libsoup. The bug has been reported to the maintainers of the library, and we can expect a fix to be released promptly.

It is crucial to stay up-to-date with vulnerability announcements and security patches, especially for widely-used libraries like libsoup. One of the effective ways to stay informed is by subscribing to security mailing lists and actively monitoring relevant forums.

Until a patch is provided, developers are advised to implement additional checks and validations for the content disposition header received in libsoup applications. Adding proper input validation checks for the parameters, including validating the existence of parameter separators like "=", can prevent NULL pointer dereference from occurring.

Conclusion

CVE-2025-32913 highlights the significance of proper input validation and maintaining up-to-date libraries in your projects. This flaw in libsoup can be easily exploited by a malicious HTTP peer, leading to denial-of-service attacks and significant disruption of services. As developers, it is our responsibility to ensure that the software we create is robust and secure, which includes patching vulnerabilities promptly and following best practices for secure coding.

For more details and updates on CVE-2025-32913, you can refer to the following original references

1. libsoup Official Website
2. CVE-2025-32913 Details on CVE Database

Timeline

Published on: 04/14/2025 14:15:24 UTC
Last modified on: 04/15/2025 18:39:27 UTC