CVE-2025-54939 is a medium severity vulnerability identified in the LiteSpeed QUIC (LSQUIC) library versions prior to 4.3.1. The vulnerability is classified under CWE-770, which pertains to the allocation of resources without limits or throttling. Specifically, the issue arises from 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, the function fails to release allocated memory appropriately, leading to a gradual increase in memory consumption over time when processing network traffic. The vulnerability has a CVSS v3.1 base score of 5.3, indicating a medium level of severity. The vector metrics reveal that the attack can be executed remotely (AV:N), requires no privileges (PR:N), and no user interaction (UI:N), with no impact on confidentiality or integrity but causing a loss of availability (A:L) due to resource exhaustion. Exploitation of this vulnerability could allow an attacker to perform a denial-of-service (DoS) attack by sending crafted QUIC packets to a server using the vulnerable LSQUIC library, causing the server to consume excessive memory and potentially crash or become unresponsive. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may require vendor updates or workarounds once available. The vulnerability affects all versions before 4.3.1, and since LSQUIC is a widely used QUIC protocol implementation by LiteSpeed Technologies, this issue could impact various web servers and applications relying on this library for QUIC support.

For European organizations, the impact of CVE-2025-54939 could be significant, especially for those operating web infrastructure or services that utilize LiteSpeed's LSQUIC library for QUIC protocol support. The memory leak can lead to denial-of-service conditions, degrading service availability and potentially causing downtime. This is particularly critical for sectors requiring high availability such as finance, e-commerce, healthcare, and public services. The vulnerability does not compromise data confidentiality or integrity but can disrupt business operations and user access. Additionally, prolonged exploitation could increase operational costs due to resource exhaustion and incident response efforts. Organizations relying on cloud services or hosting providers that use LSQUIC may also be indirectly affected. Given the remote and unauthenticated nature of the exploit, attackers can launch attacks without prior access or user interaction, increasing the risk surface. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as the vulnerability becomes publicly known and potentially weaponized.

To mitigate CVE-2025-54939, European organizations should take the following specific actions: 1) Identify and inventory all systems and applications using the LSQUIC library, particularly versions prior to 4.3.1. 2) Monitor vendor communications from LiteSpeed Technologies for patches or updates addressing this vulnerability and apply them promptly once available. 3) Implement network-level protections such as rate limiting and traffic anomaly detection to identify and block abnormal QUIC packet flows that could trigger the memory leak. 4) Employ resource monitoring and alerting on servers running LSQUIC to detect unusual memory consumption early and enable rapid response. 5) Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with signatures or heuristics targeting abnormal QUIC traffic patterns. 6) If immediate patching is not possible, evaluate temporary mitigations such as disabling QUIC support or restricting access to trusted networks to reduce exposure. 7) Conduct regular security assessments and penetration tests focusing on QUIC protocol implementations to uncover potential exploitation attempts. These measures go beyond generic advice by emphasizing proactive detection, inventory management, and network-level controls tailored to the nature of this vulnerability.