CVE-2025-55036 is an out-of-bounds write vulnerability classified under CWE-787, affecting F5 BIG-IP SSL Orchestrator when explicit forward proxy is configured on a virtual server with the proxy connect feature enabled. The vulnerability arises from improper handling of certain undisclosed traffic, which leads to memory corruption. This memory corruption can cause instability or crashes in the BIG-IP system, resulting in denial of service (DoS) conditions. The affected BIG-IP versions include 15.1.0, 16.1.0, and 17.1.0, which are widely deployed in enterprise and service provider environments for traffic management and security. The vulnerability can be exploited remotely without authentication or user interaction, increasing its risk profile. The CVSS v3.1 base score is 7.5, reflecting a high severity primarily due to the impact on availability and ease of exploitation. Although no public exploits or active attacks have been reported, the potential for disruption in critical network infrastructure is significant. The vulnerability does not affect versions that have reached End of Technical Support (EoTS). No official patches were listed at the time of publication, so mitigation relies on configuration changes and monitoring. This flaw highlights the risks associated with complex proxy configurations and the need for rigorous input validation in network security appliances.

For European organizations, the impact of CVE-2025-55036 can be substantial, particularly for those relying on F5 BIG-IP devices in their network security and traffic management infrastructure. The vulnerability can lead to memory corruption and denial of service, potentially disrupting critical services such as secure web traffic inspection, load balancing, and application delivery. This disruption could affect financial institutions, telecommunications providers, government agencies, and large enterprises that depend on BIG-IP for secure and reliable network operations. The unavailability of these services could result in operational downtime, financial losses, and reputational damage. Additionally, while the vulnerability does not directly compromise confidentiality or integrity, the resulting service outages could indirectly impact business continuity and incident response capabilities. European organizations with strict regulatory requirements around availability and service uptime, such as those governed by NIS2 Directive or GDPR, may face compliance risks if this vulnerability is exploited. The absence of known exploits currently provides a window for proactive mitigation, but the ease of remote exploitation without authentication necessitates urgent attention.

1. Immediately review and assess the configuration of BIG-IP SSL Orchestrator explicit forward proxy settings, specifically the proxy connect feature. Disable the proxy connect feature if it is not essential to your network operations. 2. Monitor network traffic for unusual or unexpected patterns that could indicate attempts to exploit this vulnerability, focusing on traffic directed at the explicit forward proxy virtual servers. 3. Engage with F5 Networks support or security advisories regularly to obtain and apply patches or firmware updates as soon as they become available for the affected BIG-IP versions. 4. Implement network segmentation and access controls to limit exposure of the BIG-IP management and proxy interfaces to trusted networks only. 5. Conduct thorough testing of BIG-IP configurations in a controlled environment before deploying changes to production to avoid inadvertent exposure. 6. Maintain up-to-date backups and incident response plans to quickly recover from potential denial of service incidents. 7. Consider deploying additional intrusion detection or prevention systems (IDS/IPS) that can identify and block exploit attempts targeting this vulnerability. 8. Educate network and security teams about this vulnerability and ensure they are prepared to respond to any signs of exploitation.