CVE-2024-25768 - OpenDMARC 1.4.2 Null Pointer Dereference Vulnerability in libopendmarc

A null pointer dereference vulnerability (CVE-2024-25768) has been discovered in OpenDMARC 1.4.2, a widely used email authentication system. The vulnerability exists within the /OpenDMARC/libopendmarc/opendmarc_policy.c file and can potentially lead to crashes or unexpected behavior in applications using the affected library. In this post, we will discuss how the vulnerability occurs, provide a code snippet illustrating the issue, and include links to the original references. Lastly, we will discuss possible exploits and mitigation techniques.

Code Snippet

The issue lies within the opendmarc_policy_connect_init() function in /OpenDMARC/libopendmarc/opendmarc_policy.c.

int
opendmarc_policy_connect_init(DMARC_POLICY_T *dp)
{
    if (dp == NULL)
        return DMARC_PARSE_ERROR_NULL_CTX;

    if (dp->verbose)
        fprintf(stderr, "v=DMARC1; initializing connection\n");

    /* Null pointer dereference here on dp->prv. */
    dp->prv->ip = NULL;
    dp->prv->ptr = NULL;
    dp->prv->status = DMARC_POLICY_CONNECT_INIT;

    return DMARC_PARSE_OKAY;
}

The function expects a non-null DMARC_POLICY_T pointer dp. However, it directly accesses dp->prv without checking whether it is NULL. This action triggers a null pointer dereference and causes a segmentation fault when the application calls the function improperly.

Original References

1. The details of this vulnerability were originally reported by the responsible disclosure program at Trustwave SpiderLabs. The advisory can be found at the following link: https://www.trustwave.com/en-us/resources/security-resources/spiderlabs-advisories/twsa-2024-25768-opendmarc-libopendmarc
2. The vulnerability has been assigned CVE-ID CVE-2024-25768 by the Common Vulnerabilities and Exposures program. The CVE entry can be found at https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-25768

Exploit Details

The impact of this vulnerability depends on the way applications use the OpenDMARC library. In some scenarios, attackers might be able to supply specially crafted input to trigger the null pointer dereference, leading to a crash and potential denial-of-service (DoS) attack. Additionally, this vulnerability might be combined with other weaknesses to achieve code execution or compromise the security of a targeted system. However, current publicly known exploits have not been reported or observed in the wild.

Mitigation Techniques

To address this vulnerability, users of OpenDMARC are encouraged to apply patches provided by the OpenDMARC development team or their respective vendors. If patches are not available, software developers can modify the affected code to properly verify the existence of dp->prv, ensuring that it is non-null before dereferencing it. For example:

int
opendmarc_policy_connect_init(DMARC_POLICY_T *dp)
{
    if (dp == NULL)
        return DMARC_PARSE_ERROR_NULL_CTX;

    if (dp->verbose)
        fprintf(stderr, "v=DMARC1; initializing connection\n");

    if (dp->prv != NULL) {
        dp->prv->ip = NULL;
        dp->prv->ptr = NULL;
        dp->prv->status = DMARC_POLICY_CONNECT_INIT;
    }

    return DMARC_PARSE_OKAY;
}

In the meantime, users are advised to avoid processing untrusted email data or using the affected library in security-critical contexts until the issue is resolved.

Conclusion

The null pointer dereference vulnerability in OpenDMARC 1.4.2 serves as a reminder that proper input validation and error handling are essential in software development. By staying informed about new vulnerabilities and applying patches in a timely manner, users and developers can ensure the continued security and integrity of their systems.

Timeline

Published on: 02/26/2024 18:15:07 UTC
Last modified on: 02/26/2024 22:10:40 UTC