In the world of cybersecurity, researchers are continuously discovering and reporting new vulnerabilities in software. One such recently identified vulnerability is CVE-2022-3116, which pertains to Heimdal's implementation of the Kerberos 5 authentication protocol. Heimdal, an open-source software package, provides key components for the implementation of the widely-used Kerberos authentication system.

This post will delve into the details of CVE-2022-3116, discussing the vulnerability's impact, the affected versions of Heimdal, example code snippets, and how an attacker could potentially exploit this vulnerability. To help understand CVE-2022-3116 better, we will link to original references and sources, thus providing you with a comprehensive analysis in simple American English.

The Vulnerability

At the core of CVE-2022-3116 lies a null pointer dereference vulnerability in Heimdal's implementation of the Kerberos 5 authentication protocol. This vulnerability can be triggered by an attacker with network access to an application that relies on the vulnerable code path. By exploiting this vulnerability, an attacker can potentially crash the application, affecting its availability and impacting the confidentiality and integrity of the data it works with.

Affected Versions

Heimdal's vulnerable implementation affects multiple versions of the software package. According to the original report, the following versions are impacted:

Heimdal 8.x series: Versions 8. to 8.7

It is crucial for users of Heimdal's Kerberos 5 implementation to update to the latest version and apply any available patches to mitigate the risks associated with CVE-2022-3116.

Code Snippet

To better grasp the vulnerability at hand, review the example code snippet below, which demonstrates how the Heimdal implementation can potentially result in a null pointer dereference:

/* Vulnerable Heimdal Kerberos 5 code path */
void vulnerable_function(krb5_authenticator *auth) {
    krb5_error_code ret;

    if (auth->checksum != NULL) {
        // Processing checksum
    } else {
        return krb5_error(KRB5KRB_AP_ERR_INAPP_CKSUM, ); // <-- Error without setting proper error object reference

    // Other vulnerable code paths leading to krb5_error calls without proper error object reference

krb5_error_code krb5_error(krb5_error_code code, krb5_error_object *error) {
    *error = malloc(sizeof(krb5_error_object)); // <-- Allocation of an error object
    if (*error == NULL)
        return KRB5KRB_ERR_GENERIC;

    // Setting error object fields
    (*error)->code = code;

    return code;

In this example, if the auth->checksum field is NULL, the vulnerable_function doesn't create a proper error object for krb5_error. Consequently, the error object reference remains NULL, and the program attempts to dereference a null pointer, leading to a crash.

Exploit Details

An attacker who can gain network access to an application implementing the vulnerable Heimdal Kerberos 5 code paths may send specially crafted packets to the application, triggering the null pointer dereference. This can result in an application crash and a denial-of-service attack, impacting both the availability and the potential confidentiality and integrity of the data being processed by the application.

Original References

1. Heimdal Security Advisory - GitHub: The official security advisory by the Heimdal project detailing the CVE-2022-3116 vulnerability and affected versions.
2. Heimdal Repository - GitHub: The main Heimdal repository on GitHub, where you can find the latest, patched version of the software package.


CVE-2022-3116 demonstrates the importance of continuously auditing and maintaining software security, as even widely-used implementations, such as Heimdal's Kerberos 5 authentication protocol, can be susceptible to vulnerabilities. By understanding these risks and applying necessary security measures, organizations can better protect their infrastructures and the users relying on them.


Published on: 03/27/2023 22:15:00 UTC
Last modified on: 04/04/2023 00:48:00 UTC