CVE-2025-20254 is a vulnerability identified in the Internet Key Exchange Version 2 (IKEv2) module of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software. The flaw arises from improper parsing of IKEv2 packets, which leads to a memory leak condition. Specifically, the vulnerability is due to the failure to release memory after its effective lifetime, causing gradual exhaustion of system memory resources. An unauthenticated remote attacker can exploit this vulnerability by sending a continuous stream of specially crafted IKEv2 packets to an affected device. This exploitation results in partial depletion of the device's memory, which in turn causes system instability. The primary impact is the inability of the device to establish new IKEv2 VPN sessions, effectively resulting in a denial of service (DoS) condition. Recovery from this state requires a manual reboot of the affected device. The vulnerability affects a wide range of Cisco ASA software versions, spanning from 9.12.1 through 9.23.1, covering multiple minor and patch releases. The CVSS v3.1 base score is 5.8, indicating a medium severity level. The vector string (AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L) highlights that the attack can be launched remotely over the network without any privileges or user interaction, and the impact is limited to availability (denial of service) with no confidentiality or integrity loss. No known exploits are reported in the wild at this time, and no patches or mitigation links were provided in the source information. The vulnerability’s scope is critical for environments relying on Cisco ASA devices for VPN connectivity and network security, as disruption of VPN services can severely impact secure communications and business continuity.

For European organizations, the impact of CVE-2025-20254 can be significant due to the widespread use of Cisco ASA devices in enterprise and governmental networks for VPN and firewall services. The denial of service condition caused by memory exhaustion can disrupt secure remote access, which is critical for business operations, especially in the context of increased remote work and cross-border communications within Europe. Loss of VPN connectivity can lead to operational downtime, reduced productivity, and potential exposure to additional security risks if fallback or less secure communication methods are used. Critical infrastructure sectors such as finance, healthcare, energy, and public administration that rely on Cisco ASA for secure communications are particularly vulnerable. The requirement for a manual reboot to recover from the DoS condition means that automated failover or recovery mechanisms may not be sufficient, potentially prolonging service outages. Additionally, the vulnerability can be exploited without authentication or user interaction, increasing the risk of opportunistic attacks from external threat actors. While no data confidentiality or integrity is directly compromised, the availability impact alone can cause cascading effects on dependent services and compliance with regulatory requirements such as GDPR, which mandates maintaining secure and reliable IT systems.

1. Immediate deployment of Cisco’s official patches or updates once available is the most effective mitigation. Organizations should monitor Cisco security advisories closely for patch releases addressing this vulnerability. 2. Implement network-level filtering to restrict and monitor incoming IKEv2 traffic to trusted sources only, using access control lists (ACLs) or firewall rules to limit exposure to untrusted or public networks. 3. Deploy rate limiting or traffic anomaly detection mechanisms on VPN gateways to detect and block abnormal volumes of IKEv2 packets that could indicate exploitation attempts. 4. Utilize redundant VPN gateways with load balancing and failover capabilities to minimize service disruption in case one device becomes unstable due to exploitation. 5. Regularly audit and update VPN configurations to ensure minimal exposure and adherence to best practices, including disabling unused VPN protocols or services. 6. Establish robust incident response procedures to quickly identify and respond to DoS conditions, including automated alerts for VPN service degradation and readiness for manual device reboot if necessary. 7. Consider network segmentation to isolate critical VPN infrastructure from less trusted network segments, reducing the attack surface. 8. Engage with Cisco support for guidance on interim workarounds or configuration changes that may reduce risk prior to patch availability.