CVE-2025-20252 is a medium severity vulnerability affecting the Internet Key Exchange Version 2 (IKEv2) module within Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software. The vulnerability arises from improper parsing of IKEv2 packets, which leads to a memory leak condition. Specifically, the affected software versions fail to release allocated memory after the effective lifetime of certain IKEv2 sessions or packets has expired. An unauthenticated, remote attacker can exploit this flaw by sending a continuous stream of specially crafted IKEv2 packets to the targeted device. This causes the device to gradually exhaust its available system memory, leading to resource depletion. As a result, the device becomes unstable and is unable to establish new IKEv2 VPN sessions, effectively causing a denial of service (DoS) condition. Recovery from this state requires a manual reboot of the affected device. The vulnerability affects a broad range of Cisco ASA software versions, spanning from 9.8.4.x through 9.23.1, indicating a long-standing issue across multiple releases. The CVSS v3.1 base score is 5.8, reflecting a medium severity level, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impact limited to availability (A:L) without affecting confidentiality or integrity. No known exploits are reported in the wild as of the publication date (August 14, 2025). This vulnerability primarily impacts the availability of VPN services relying on IKEv2 on Cisco ASA and FTD devices, which are widely deployed in enterprise and service provider networks for secure remote access and site-to-site VPN connectivity.

For European organizations, the impact of CVE-2025-20252 can be significant, particularly for those relying heavily on Cisco ASA or FTD devices for VPN connectivity and network perimeter security. The vulnerability can be exploited remotely without authentication, making it a viable vector for denial of service attacks that disrupt VPN availability. This disruption can prevent remote employees, partners, or branch offices from securely connecting to corporate networks, potentially halting critical business operations, especially in sectors like finance, healthcare, government, and critical infrastructure where secure remote access is essential. The requirement for a manual reboot to recover from the DoS condition may lead to extended downtime and operational disruption. Additionally, repeated exploitation attempts could degrade network performance and stability over time. Although confidentiality and integrity are not directly impacted, the loss of availability can indirectly affect business continuity and compliance with regulatory requirements such as GDPR, which mandates maintaining secure and reliable access controls. The widespread use of Cisco ASA devices across European enterprises and service providers increases the potential attack surface, making this vulnerability a notable risk in the region.

To mitigate the risk posed by CVE-2025-20252, European organizations should take the following specific actions: 1) Identify and inventory all Cisco ASA and FTD devices in their environment, noting software versions to determine exposure. 2) Apply the latest Cisco patches or software updates that address this vulnerability as soon as they become available. Since no patch links were provided, organizations should monitor Cisco’s official security advisories and update promptly. 3) Implement network-level protections such as rate limiting or firewall rules to restrict or throttle incoming IKEv2 traffic from untrusted or external sources, reducing the risk of continuous crafted packet streams. 4) Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or anomaly detection capabilities tuned to detect abnormal IKEv2 packet patterns indicative of exploitation attempts. 5) Establish robust monitoring and alerting for VPN service availability and device memory utilization to detect early signs of exploitation or resource exhaustion. 6) Develop and test incident response procedures that include rapid device reboot and recovery steps to minimize downtime. 7) Consider segmenting VPN infrastructure and limiting exposure of ASA/FTD management interfaces to reduce attack vectors. 8) Educate network operations teams about this vulnerability and ensure readiness to respond to potential DoS incidents. These targeted mitigations go beyond generic advice by focusing on proactive detection, traffic control, and operational readiness specific to the nature of this memory leak vulnerability in IKEv2 processing.