CVE-2024-26462 - Memory Leak Vulnerability in Kerberos 5 v1.21.2: Explanation, Exploit, and Mitigation

Kerberos is a widely used network authentication protocol designed to provide strong authentication for client/server applications over insecure networks, primarily using secret-key cryptography. The Kerberos version 5 (also known as krb5) is the latest iteration of the protocol, which is widely used by applications for authentication purposes.

A newly discovered vulnerability (CVE-2024-26462) in krb5 1.21.2 has important implications for the security and integrity of the protocol, as it could potentially lead to memory leaks in the affected systems. This post will provide an overview of the vulnerability, explore a code snippet with the memory leak issue, offer references to the original research, explain the practical impact of the vulnerability, and suggest ways to mitigate the problem.

Memory Leak Vulnerability in krb5 1.21.2

In krb5 1.21.2, a memory leak vulnerability was found in the /krb5/src/kdc/ndr.c file. The vulnerability resides in a specific function, where the memory allocated during execution is improperly managed, leading to a gradual increase in memory consumption. Over time, this memory leak issue can cause the affected system to run out of memory and become unstable, consequently leading to potential service disruptions or exploitation by malicious actors.

Original references investigating the memory leak can be found at the following links

1. MIT krb5 repository commit where the issue was fixed
2. Mitigation steps and technical details in the krb5 documentation

The following code snippet demonstrates the memory leak vulnerability in /krb5/src/kdc/ndr.c

int process_ndr_request(struct connection *conn, const krb5_data *req, krb5_data *rep)
{
    int ret = ;
    krb5_error_code err;
    krb5_data state_buf = empty_data();
    KdcRequestState state;

    /* ... */

    err = decode_kdc_request(conn, req, &state, &state_buf);
    if (err) {
        ret = make_error_response(state_buf.request_tid, err, rep);
        goto cleanup;
    }
    /* ... */

cleanup:
    free_kdc_request_state(state);
    free_data_contents(conn->ctx, &state_buf);
    return ret;
}

In this snippet, the memory allocated during the 'decode_kdc_request()' function call is not properly freed in the 'cleanup' section, leading to the memory leak issue.

Exploit Details

The memory leak vulnerability (CVE-2024-26462) has the potential to be exploited by malicious actors who can flood the affected system with requests specifically designed to trigger the memory leak issue. By repeatedly sending these requests to the affected Kerberos server, an attacker can consume the system's memory resources, causing service disruptions or even gaining unauthorized access to the system if the memory leak leads to further vulnerabilities.

Mitigation

To address the memory leak vulnerability in krb5 1.21.2, users and administrators should consider employing the following mitigation options:

1. Upgrade to a newer version of Kerberos that contains the fix for the memory leak issue. In the meantime, users can follow the MIT krb5 repository to track the progress of the fix and its release.
2. Monitor the memory usage of Kerberos servers and restart them if a significant increase in memory consumption is observed. This may help alleviate the impact of the memory leak issue until a more permanent fix is available.
3. Guard the Kerberos servers behind firewalls or other security measures to limit access and reduce the possibility of exploitation by malicious actors.

Conclusion

The memory leak vulnerability (CVE-2024-26462) in krb5 1.21.2 is a serious issue that can lead to service disruptions or potential exploitation by malicious actors. Users and administrators of Kerberos servers should take proactive steps to mitigate the vulnerability by upgrading their software, monitoring memory usage, and implementing additional security measures. By staying informed about the latest developments and taking prompt action to address vulnerabilities, the security and integrity of the Kerberos protocol can be maintained.

Timeline

Published on: 02/29/2024 01:44:18 UTC
Last modified on: 05/14/2024 15:09:01 UTC