CVE-2024-1441: Off-by-one Error in udevListInterfacesByStatus() Function Leads to Denial of Service Attack Against Libvirt Daemon

A vulnerability has been discovered in the popular virtualization library, libvirt, that allows an attacker to crash the libvirt daemon when the number of interfaces exceeds the size of the names array used in the udevListInterfacesByStatus() function. This flaw was assigned the CVE identifier CVE-2024-1441, implying its severity and potential impact on affected systems. This vulnerability could lead to a denial of service (DoS) attack, rendering affected systems unresponsive or unstable.

The objective of this long-read post is to offer a comprehensive understanding of CVE-2024-1441, including an explanation of the vulnerability, how to reproduce it, and potential mitigation strategies. Links to the original reports and references will also be provided to give readers valuable resources for further study.

Vulnerability Details

The vulnerability is due to an off-by-one error in the udevListInterfacesByStatus() function within the libvirt library. When a specific portion of code within this function is executed, it may lead to the libvirt daemon crashing if the number of interfaces exceeds the size of the names array.

The origin of the vulnerability is linked to an integral value comparison within a loop iterator in the udevListInterfacesByStatus() function. The following code snippet demonstrates the vulnerability:

    int udevListInterfacesByStatus(virConnectPtr conn,
                                    VIR_IF_STATE state,
                                    char ***const names,
                                    int maxnames)
    {
        /* ... */
        for (i = ; i < maxnames; i++) {
            /* ... */
            if (state != VIR_IF_STATE_UNKNOWN && state != iface->state)
                continue;

            if (num_ifs >= maxnames) {
                break;
            }
            /* ... */
        }
        /* ... */
    }

In the above code snippet, the loop runs up to maxnames, which represents the size of the names array. Continuing with the given example, if num_ifs is equal to maxnames, the control breaks out of the loop. This behavior leads to the off-by-one error and would result in an attempt to write one past the end of the names array.

Exploitation of this vulnerability can be achieved by sending specially crafted data to the libvirt daemon, causing a crash and enabling an unprivileged client to execute a denial of service attack.

Configure a system with libvirt, ensuring that the version contains the vulnerable code.

2. Prepare an exploit that sends specially crafted data to libvirt by manipulating the state and number of virtual network interfaces.

Original References

- Official CVE details: https://nvd.nist.gov/vuln/detail/CVE-2024-1441
- Libvirt mailing list discussion: https://www.redhat.com/archives/libvir-list/2024-March/msg00000.html
- Bugzilla report: https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2024-1441

To protect against this CVE-2024-1441 vulnerability, consider the following mitigation strategies

1. Apply the appropriate patches provided by the libvirt development team or your Linux distribution maintainers.
2. As a short-term workaround, restrict unprivileged access to the libvirt daemon by configuring your system to allow only trusted users.
3. Frequently check for updates from the libvirt maintainers to stay up-to-date with the latest security fixes.

Conclusions

The CVE-2024-1441 vulnerability poses a significant risk to systems running vulnerable versions of the libvirt library, potentially causing denial of service attacks. By understanding the issue, reproducing it, and employing the mitigations detailed in this post, you can minimize the threat and keep your systems secure. Stay vigilant and follow the latest security updates from libvirt maintainers to stay ahead of potential threats.

Timeline

Published on: 03/11/2024 14:15:06 UTC
Last modified on: 04/01/2024 13:17:00 UTC