CVE-2025-20355 is a vulnerability classified as an 'Open Redirect' in the web-based management interface of Cisco Digital Network Architecture Center (DNA Center), specifically affecting the Cisco Catalyst Center Virtual Appliance component. The root cause is improper input validation of HTTP request parameters, which allows an unauthenticated, remote attacker to manipulate HTTP requests intercepted from users and redirect them to arbitrary, potentially malicious websites. This vulnerability does not require authentication but does require user interaction, such as clicking on a crafted URL or link. The attacker can exploit this by intercepting legitimate HTTP requests and modifying the URL parameters to point to an untrusted external site. The vulnerability affects a broad range of Cisco DNA Center versions, from early releases like 1.0.0.0 up to recent 2.3.7.x versions, including various AIRGAP and MDNAC variants, indicating a long-standing issue across multiple product iterations. The CVSS v3.1 base score is 4.7, categorized as medium severity, with vector metrics indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), required user interaction (UI:R), scope changed (S:C), no confidentiality impact (C:N), low integrity impact (I:L), and no availability impact (A:N). The scope change indicates that the vulnerability affects components beyond the initially vulnerable component, potentially impacting the broader system context. No known exploits are currently reported in the wild, and no patches are explicitly linked in the provided data, suggesting that organizations should monitor Cisco advisories for updates. The vulnerability primarily facilitates phishing or social engineering attacks by redirecting users to malicious sites, potentially leading to credential theft or malware delivery if users are deceived. However, it does not directly compromise system confidentiality or availability. Given the nature of Cisco DNA Center as a network management platform widely used in enterprise and service provider environments, exploitation could undermine user trust and lead to secondary attacks.

For European organizations, the primary impact of CVE-2025-20355 lies in the potential for phishing and social engineering attacks facilitated by malicious redirection. Since Cisco DNA Center is widely deployed in enterprise networks for managing network infrastructure, attackers exploiting this vulnerability could redirect network administrators or users accessing the management interface to malicious sites designed to harvest credentials or deliver malware. While the vulnerability itself does not grant direct access or control over network devices, successful exploitation could serve as a stepping stone for further compromise. The integrity of user sessions and trust in the management interface could be undermined, potentially leading to operational disruptions if attackers leverage stolen credentials or deploy malware. Given the extensive list of affected versions, many organizations may be running vulnerable instances, increasing the attack surface. The medium severity rating reflects that while the vulnerability is not directly critical, the indirect consequences through user deception can be significant, especially in environments with high-value network assets. Additionally, the requirement for user interaction means that effective user awareness and security controls can mitigate risk. The lack of known exploits in the wild reduces immediate risk but does not preclude future exploitation attempts. European organizations with critical infrastructure or large-scale network deployments using Cisco DNA Center should prioritize addressing this vulnerability to maintain operational security and prevent phishing-related incidents.

1. Monitor Cisco's official security advisories and apply patches or updates as soon as they become available for Cisco DNA Center versions affected by CVE-2025-20355. 2. Implement strict input validation and sanitization on any web-facing components or proxies that handle requests to Cisco DNA Center to detect and block malicious URL parameters that could trigger open redirects. 3. Configure web application firewalls (WAFs) or reverse proxies to enforce URL whitelisting or block redirection to untrusted domains. 4. Educate network administrators and users with access to Cisco DNA Center about the risks of clicking on unsolicited or suspicious links, emphasizing verification of URLs before interaction. 5. Employ multi-factor authentication (MFA) on Cisco DNA Center access to reduce the impact of credential theft resulting from phishing attacks leveraging this vulnerability. 6. Conduct regular security awareness training focused on phishing and social engineering to reduce successful exploitation via user interaction. 7. Review and restrict network access to Cisco DNA Center management interfaces to trusted IP ranges or VPNs to limit exposure to external attackers. 8. Monitor logs and network traffic for unusual redirection patterns or access attempts that could indicate exploitation attempts. 9. Consider deploying browser security policies or extensions that warn users about suspicious redirects or untrusted domains. 10. Maintain an incident response plan that includes procedures for handling phishing or redirection-based attacks targeting network management platforms.