CVE-2025-11230 is a vulnerability categorized under CWE-407 (Inefficient Algorithmic Complexity) found in the mjson component of HAProxy Community Edition versions 2.4.0 through 3.2.0. The flaw arises because the JSON parsing algorithm used by HAProxy does not efficiently handle certain crafted JSON inputs, leading to excessive computational resource consumption. This inefficiency can be exploited remotely by attackers who send specially crafted JSON requests to HAProxy instances exposed to the network. The result is a denial of service (DoS) condition where the HAProxy process becomes overwhelmed, potentially leading to service unavailability. The vulnerability does not affect confidentiality or integrity, as it does not allow data leakage or unauthorized data modification. No authentication or user interaction is required, making exploitation straightforward for any attacker with network access to the HAProxy service. The CVSS v3.1 base score of 7.5 reflects a high severity due to network attack vector, low complexity, no privileges required, and a significant impact on availability. Currently, there are no publicly known exploits in the wild, and no patches have been linked yet, indicating that organizations must rely on mitigations until official fixes are released. HAProxy is widely used in European enterprises and service providers for load balancing and proxying HTTP/HTTPS traffic, making this vulnerability particularly relevant for critical infrastructure and high-availability environments.

For European organizations, the primary impact of CVE-2025-11230 is the potential for denial of service against critical network infrastructure components. HAProxy is commonly deployed in data centers, cloud environments, and edge networks to manage traffic load and ensure service availability. Exploitation could disrupt web services, internal applications, and APIs, leading to operational downtime and potential financial losses. The lack of confidentiality or integrity impact means data breaches are unlikely, but service interruptions can affect customer trust and compliance with service-level agreements (SLAs). Organizations in sectors such as finance, telecommunications, government, and e-commerce, which rely heavily on HAProxy for traffic management, are at heightened risk. Additionally, the ease of exploitation without authentication increases the threat landscape, as attackers can launch DoS attacks from remote locations without insider access. The absence of known exploits currently provides a window for proactive defense, but the vulnerability’s presence in multiple recent HAProxy versions means many deployments remain exposed.

Until official patches are released, European organizations should implement several targeted mitigations to reduce risk. First, deploy network-level rate limiting and filtering to detect and block abnormal JSON request patterns that could trigger the inefficient parsing. Use web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to identify and mitigate suspicious JSON payloads. Monitor HAProxy logs for unusual spikes in JSON request processing times or resource consumption to enable early detection of exploitation attempts. Consider isolating HAProxy instances behind additional proxy layers or VPNs to restrict exposure to untrusted networks. Regularly update HAProxy to the latest stable versions once patches addressing this vulnerability become available. Engage with HAProxy Technologies and community channels for timely vulnerability disclosures and fixes. Finally, conduct internal audits of HAProxy configurations to ensure minimal exposure of JSON parsing endpoints and enforce strict input validation where possible.