CVE-2025-20365 is a vulnerability in the IPv6 Router Advertisement (RA) packet processing logic within Cisco Aironet Access Point Software running on IOS XE Controllers. The root cause is a logic error that fails to properly verify the source of IPv6 RA packets received from wireless clients. An attacker who can associate with the wireless network can send specially crafted IPv6 RA packets to the affected device. This allows the attacker to temporarily alter the IPv6 gateway setting on the access point, effectively redirecting IPv6 traffic. While the attack does not grant direct access to data or cause device crashes, it can disrupt network operations by causing intermittent packet loss for wireless clients relying on the compromised gateway. The vulnerability affects a broad range of IOS XE versions, including 16.10.x through 17.15.1, indicating a long-standing issue across multiple releases. Exploitation requires adjacency (wireless association) but no authentication or user interaction, lowering the barrier for attackers physically near the network. No public exploits or active exploitation have been reported, but the potential for network disruption exists. The CVSS v3.1 score is 4.3 (medium), reflecting limited impact on confidentiality and availability but a notable integrity impact due to gateway manipulation.

For European organizations, this vulnerability poses a risk primarily to the integrity and reliability of wireless network operations. Organizations relying on Cisco Aironet access points with affected IOS XE versions may experience intermittent packet loss and network instability due to manipulated IPv6 routing. This can degrade user experience, disrupt critical business applications, and complicate network troubleshooting. While the vulnerability does not directly expose sensitive data or cause denial of service, the temporary gateway changes could be leveraged as part of a broader attack chain, such as man-in-the-middle attacks or traffic interception if combined with other vulnerabilities. Sectors with high reliance on wireless connectivity—such as finance, healthcare, government, and manufacturing—may face operational disruptions. The requirement for attacker adjacency limits remote exploitation but does not eliminate risk in environments with guest or poorly segmented wireless networks. Given the widespread deployment of Cisco Aironet devices in Europe, the vulnerability could affect a significant number of enterprises and public institutions.

European organizations should prioritize patching affected Cisco IOS XE Controller versions as soon as Cisco releases security updates addressing CVE-2025-20365. Until patches are available, network administrators should implement strict wireless network segmentation and access controls to limit unauthorized client association. Employing network access control (NAC) solutions can help ensure only trusted devices connect to wireless networks. Monitoring IPv6 RA traffic for anomalies or unexpected gateway advertisements can provide early detection of exploitation attempts. Disabling IPv6 Router Advertisement processing on wireless interfaces where not required can mitigate risk. Additionally, organizations should review wireless client isolation settings to prevent clients from sending RA packets to access points. Regularly auditing wireless infrastructure configurations and maintaining up-to-date firmware will reduce exposure. Incident response teams should be prepared to investigate intermittent connectivity issues that may indicate exploitation attempts.