CVE-2025-20365 is a vulnerability identified in Cisco Aironet Access Point Software running on IOS XE Controller platforms. The flaw arises from improper verification of the source of IPv6 Router Advertisement (RA) packets. Specifically, the software contains a logic error in processing IPv6 RA packets received from wireless clients. An unauthenticated attacker, located adjacent to the vulnerable device (i.e., within wireless range), can exploit this by associating with the wireless network and sending crafted IPv6 RA packets. Successful exploitation allows the attacker to temporarily modify the IPv6 gateway setting on the affected access point. This manipulation can disrupt normal network routing behavior, causing intermittent packet loss for wireless clients connected to the compromised access point. The vulnerability affects a wide range of Cisco Aironet software versions, spanning multiple major releases (16.x and 17.x branches). The CVSS v3.1 base score is 4.3 (medium severity), reflecting that the attack vector is adjacent network, requires no privileges or user interaction, and impacts integrity but not confidentiality or availability. No known exploits are reported in the wild as of the publication date. The vulnerability primarily impacts the integrity of network routing configurations on affected devices, potentially degrading wireless network performance and reliability temporarily but does not directly lead to data disclosure or device takeover. However, the ability to alter routing could be leveraged as part of more complex attack chains, such as man-in-the-middle attacks or denial of service through network disruption.

For European organizations, this vulnerability poses a risk to the stability and reliability of wireless network infrastructure, especially in environments heavily reliant on Cisco Aironet access points with affected IOS XE versions. Temporary modification of the IPv6 gateway can cause intermittent packet loss, leading to degraded user experience, potential disruption of critical business applications, and increased support costs. Organizations with IPv6-enabled wireless networks are particularly vulnerable. While the vulnerability does not directly expose sensitive data or allow device compromise, the induced network instability could be exploited by threat actors to facilitate further attacks, such as intercepting traffic or causing denial of service conditions. This is especially relevant for sectors with high dependence on wireless connectivity, such as finance, healthcare, education, and government institutions across Europe. The medium severity rating suggests that while the threat is not critical, it should not be ignored, particularly in large-scale deployments where even temporary outages can have significant operational impact.

To mitigate this vulnerability, European organizations should: 1) Identify and inventory all Cisco Aironet access points running affected IOS XE software versions. 2) Apply Cisco's official patches or software updates as soon as they become available to address CVE-2025-20365. In the absence of patches, consider temporary workarounds such as disabling IPv6 Router Advertisement processing from wireless clients if feasible. 3) Implement network segmentation and strict wireless client authentication to limit the ability of unauthorized devices to associate with wireless networks, thereby reducing the attack surface. 4) Monitor wireless network traffic for anomalous IPv6 RA packets or unusual changes in gateway configurations to detect potential exploitation attempts early. 5) Employ network intrusion detection systems (NIDS) with IPv6 RA anomaly detection capabilities. 6) Educate network administrators about this vulnerability and ensure incident response plans include procedures for addressing IPv6-related network disruptions. These targeted actions go beyond generic advice by focusing on IPv6 RA packet handling, wireless client controls, and proactive monitoring specific to the nature of this vulnerability.