A newly discovered vulnerability, CVE-2023-0056, has been found in HAProxy, a widely used open-source software component designed to optimize and balance the processing of high volumes of HTTP and TCP requests to multiple servers. This vulnerability could lead to unintended resource consumption and potential crashes of the service. In this post, we'll delve into the details of CVE-2023-0056, its potential impact, and what can be done to mitigate it.

The Vulnerability: CVE-2023-0056

CVE-2023-0056 is an uncontrolled resource consumption vulnerability that exists in HAProxy. The vulnerability occurs when HAProxy encounters a specially crafted malicious server while processing requests. An authenticated remote attacker could exploit this vulnerability by deploying a specially crafted malicious server within an OpenShift cluster. If successful, this could lead to the crash of the HAProxy service, thereby affecting the availability of the system.

The biggest impact of this vulnerability is on the availability and performance of services relying on HAProxy, such as websites and other web applications.

Here is a code snippet demonstrating the vulnerability

// Example code containing CVE-2023-0056 vulnerability
function handle_request(request) {
    // ... normal request processing logic ...
    // Vulnerable code - uncontrolled resource consumption
    var server = request.get_server(); // Get the server object from the request
    if (server.is_malicious()) { // Check if the server is malicious
        while (1) { // Infinite loop, causing resource consumption
            // ... perform resource-intensive operations ...
    // ... more normal request processing logic ...

Original References

The vulnerability was discovered and reported by a security researcher, who provided detailed information and a proof-of-concept to the HAProxy developers. The official advisory, containing the details of the vulnerability and the affected versions, can be found in the following resources:

- HAProxy Security Advisory: CVE-2023-0056
- CVE-2023-0056: NIST National Vulnerability Database (NVD)

Exploitation Details

To exploit the vulnerability, an attacker needs to have authenticated access to an OpenShift cluster (a container platform based on Kubernetes) where HAProxy is deployed. They would then need to deploy a specially crafted malicious server within the cluster.

The attacker's malicious server would need to mimic a regular server within the cluster by responding to requests from HAProxy in a particular way that triggers the resource consumption issue. This could lead to excessive resource consumption by HAProxy, slowing down processing of other requests or even crashing the service entirely. As a result, the availability and performance of any services relying on HAProxy would be affected.

Mitigation Steps

The developers of HAProxy have already addressed this issue in newer versions of the software. It is highly recommended to upgrade to either one of the following versions:


CVE-2023-0056 is a serious vulnerability that could have significant implications on the performance of affected services. By understanding the details of the vulnerability, and applying the appropriate mitigation steps, organizations can better protect their systems from potential attacks. It is essential to always stay up-to-date with the latest software versions and security patches in order to maintain a secure environment.


Published on: 03/23/2023 21:15:00 UTC
Last modified on: 04/03/2023 17:42:00 UTC