External risk intelligence

OpenVPN Use After Free Memory Leak and Remote Execution Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2023-46850

OpenVPN is a remote access technology designed to be internet-facing for the purpose of establishing secure connections. As a VPN gateway, it is inherently intended to accept traffic from remote peers across the public internet, making the service's network interface a primary, public-facing entry point in standard deployments.

Use After Free

Openvpn

2.6.0 to 2.6.62.11.0 to 2.11.32.12.0 to before 2.12.212.039

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability in OpenVPN software could allow an unauthenticated attacker to compromise systems. This issue arises from a flaw in how the software handles network data, potentially leading to memory leaks or the execution of malicious code remotely. The main concern is to confirm if your organization uses the affected versions of OpenVPN.

A software flaw can expose systems to risk.
OpenVPN is a widely used remote access tool.
Confirm OpenVPN usage and versions.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending specially crafted network data to an exposed OpenVPN service. This could allow them to trigger a use-after-free condition, potentially leading to the disclosure of memory contents or even remote code execution.

No authentication needed to access.
Sending malicious network buffers.
Memory leak or remote execution.

Live Threat

Current exploitation, exposure, and threat context

The use-after-free vulnerability in OpenVPN could allow an unauthenticated attacker to cause undefined behavior or potentially execute arbitrary code by sending specially crafted network buffers to a vulnerable server. This could expose memory contents or lead to a compromise of the service.

Memory buffers or service control may be exposed.
Malicious network packets could trigger the vulnerability.
Service disruption or unauthorized code execution may occur.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in OpenVPN affects organizations utilizing its community or Access Server products. The primary responsibility for addressing this issue likely falls to the platform or infrastructure teams managing the VPN service, with coordination from the security team for exposure assessment and vendor management if commercial support is involved. The immediate first step is to inventory all instances of the affected OpenVPN software, determine their exposure to the network, and identify the business-criticality and ownership of each deployment to prioritize remediation efforts.

Identify and triage affected OpenVPN deployments.
Verify external reachability and criticality.
Coordinate vendor advisories and plan remediation.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is OpenVPN and how is it used?

OpenVPN is a widely deployed, open-source technology used to create secure, encrypted network tunnels. It acts as a gateway, allowing remote users or branch offices to connect safely to a private network over the public internet. Because it provides remote access, it is commonly installed on servers that must remain reachable from outside the local network.

What does use-after-free mean in CVE-2023-46850?

This vulnerability is a 'use-after-free' error, classified as CWE-416. It occurs when software continues to use a pointer to a memory location after that memory has been freed or cleared. In this case, when the software incorrectly manages these memory buffers during network communication, it can lead to unpredictable behavior, such as leaking sensitive memory contents or allowing an attacker to run their own unauthorized code on the system.

How is this OpenVPN vulnerability triggered?

An attacker triggers this flaw by sending specially crafted network data to a vulnerable OpenVPN service. The vulnerability relies on the way the server processes these incoming network buffers from a remote peer. It is important to note that this condition is triggered by the transmission of network traffic itself; it does not require an attacker to have a valid user account or prior authentication to the VPN service to attempt the attack.

Is my organization at risk according to Halo Surface Signal?

Halo Surface Signal identifies that OpenVPN is typically deployed as an internet-facing service, meaning its network interfaces are intentionally exposed to the public internet to facilitate remote connections. Because of this design, any instance of the software running an affected version is considered to have an external attack surface, making it directly reachable for exploitation by unauthorized remote actors.

What are the first steps to address CVE-2023-46850?

Start by creating an inventory of all OpenVPN and OpenVPN Access Server deployments within your environment to identify which systems are running the vulnerable versions. Once you have a list, determine which of these services are exposed to the internet and assess their business criticality. Coordinate with your infrastructure teams to prioritize patching these specific instances, starting with those that are most accessible to external traffic.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.