CVE-2025-54500 is a vulnerability in the HTTP/2 protocol implementation within F5 BIG-IP devices, specifically related to the handling of HTTP/2 control frames. The flaw allows an attacker to send malformed HTTP/2 control frames that break the enforcement of the maximum concurrent streams limit, a key mechanism designed to prevent resource exhaustion on the server. This vulnerability is categorized under CWE-770, which involves allocation of resources without proper limits or throttling, leading to potential denial-of-service (DoS) conditions. The attack, dubbed the HTTP/2 MadeYouReset attack, exploits this weakness by overwhelming the BIG-IP device with excessive concurrent streams beyond the configured limit, causing it to allocate resources excessively and ultimately degrade or disrupt service availability. The vulnerability affects multiple supported versions of BIG-IP (15.1.0, 16.1.0, 17.1.0, and 17.5.0), but does not impact versions that have reached End of Technical Support. The CVSS v3.1 base score is 5.3 (medium severity), reflecting a network attack vector with low complexity, no privileges or user interaction required, and impact limited to availability. No known exploits have been reported in the wild, and no official patches have been released at the time of publication. The vulnerability's exploitation could lead to denial of service for applications and services relying on BIG-IP for load balancing and application delivery, potentially affecting business continuity and user experience.

For European organizations, the primary impact of CVE-2025-54500 is the risk of denial-of-service attacks against critical network infrastructure that uses F5 BIG-IP devices. These devices are widely deployed in enterprise environments for load balancing, application delivery, and security functions. A successful attack could disrupt availability of web applications, internal services, and customer-facing portals, leading to operational downtime and potential financial losses. Sectors such as finance, telecommunications, government, and healthcare, which often rely on BIG-IP for high availability and security, could experience significant service interruptions. Additionally, the disruption could affect compliance with service-level agreements (SLAs) and regulatory requirements related to uptime and incident response. Although confidentiality and integrity are not directly impacted, the availability degradation could indirectly affect business operations and trust. The lack of authentication or user interaction requirements makes the attack feasible from remote locations, increasing the threat surface for European organizations with internet-facing BIG-IP deployments.

1. Monitor network traffic for abnormal HTTP/2 behavior, specifically unusually high numbers of concurrent streams or malformed control frames, using advanced intrusion detection systems or network monitoring tools. 2. Implement rate limiting or throttling at the network edge or load balancer level to restrict the number of concurrent HTTP/2 streams accepted from a single client or IP address. 3. Deploy web application firewalls (WAFs) capable of inspecting HTTP/2 traffic and blocking malformed or suspicious control frames. 4. Segment and isolate BIG-IP management and control interfaces from untrusted networks to reduce exposure. 5. Maintain up-to-date inventories of BIG-IP versions in use and prioritize patching or upgrading to versions that address this vulnerability once available. 6. Engage with F5 support or security advisories regularly to obtain patches or recommended configuration changes. 7. Consider temporary disabling or limiting HTTP/2 support on BIG-IP devices if feasible and if the risk of DoS outweighs the benefits of HTTP/2 performance. 8. Conduct regular penetration testing and vulnerability assessments focused on HTTP/2 implementations to identify and remediate weaknesses proactively.