CVE-2025-54939 is a medium-severity vulnerability affecting the LiteSpeed QUIC (LSQUIC) library versions prior to 4.3.1. The vulnerability is classified under CWE-770, which involves the allocation of resources without proper limits or throttling. Specifically, the issue is a memory leak in the function lsquic_engine_packet_in. This function is responsible for processing incoming QUIC packets within the LSQUIC engine. Due to improper handling, memory allocated during packet processing is not correctly freed, leading to a gradual increase in memory usage over time. The vulnerability has a CVSS 3.1 base score of 5.3, indicating a medium impact level. The vector indicates that the attack can be performed remotely (AV:N), requires no privileges (PR:N), and no user interaction (UI:N). The impact is limited to availability (A:L), with no confidentiality or integrity loss. There are no known exploits in the wild, and no patches have been linked yet, suggesting that the issue is newly disclosed or pending remediation. The vulnerability could be exploited by an attacker sending a high volume of crafted QUIC packets to a server using the vulnerable LSQUIC library, causing the server's memory consumption to grow uncontrollably. This could lead to denial of service (DoS) conditions due to resource exhaustion, impacting service availability. Since QUIC is a transport layer network protocol widely used to improve web performance and security, servers and applications relying on LSQUIC for QUIC support are at risk. The vulnerability does not require authentication or user interaction, making it easier to exploit remotely. However, the absence of confidentiality or integrity impact limits the scope to availability degradation only.

For European organizations, the primary impact of CVE-2025-54939 is the potential for denial of service attacks targeting services using the LSQUIC library for QUIC protocol support. This can affect web servers, content delivery networks, and other network infrastructure components that rely on LSQUIC to handle QUIC traffic. The memory leak can cause servers to consume excessive memory, leading to crashes or degraded performance, disrupting business operations and online services. This is particularly critical for sectors with high availability requirements such as financial services, e-commerce, telecommunications, and government services. The medium severity score reflects that while confidentiality and integrity are not compromised, availability issues can still cause significant operational disruptions and potential financial losses. Additionally, the ease of remote exploitation without authentication increases the risk of opportunistic attacks. European organizations that have adopted QUIC-enabled services using LSQUIC may face increased risk of service outages or degraded user experience. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once patches are released or if organizations delay remediation.

1. Immediate identification of all systems and services using the LSQUIC library for QUIC support is critical. This includes web servers, proxies, and any custom applications integrating LSQUIC. 2. Monitor memory usage patterns on these systems to detect abnormal increases that could indicate exploitation attempts. 3. Apply updates or patches from LiteSpeed Technologies as soon as they become available. Since no patch links are currently provided, maintain close communication with the vendor for timely updates. 4. Implement network-level rate limiting and filtering to restrict the volume of incoming QUIC packets from untrusted sources, reducing the risk of resource exhaustion. 5. Use Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) capable of detecting anomalous QUIC traffic patterns. 6. Consider deploying redundancy and failover mechanisms to maintain service availability in case of DoS conditions. 7. For critical infrastructure, conduct penetration testing and vulnerability assessments focusing on QUIC implementations to proactively identify exploitation attempts. 8. Educate network and security teams about this vulnerability to ensure rapid detection and response. 9. If feasible, temporarily disable QUIC support on vulnerable systems until patches are applied, balancing performance and security needs.