CVE-2025-20342 is a medium-severity stored cross-site scripting (XSS) vulnerability affecting Cisco Unified Computing System (UCS) Managed versions including a wide range of 3.x and 4.x releases. The vulnerability resides in the Virtual Keyboard Video Monitor (vKVM) connection handling component of the Cisco Integrated Management Controller (IMC), which is part of the UCS Manager. Specifically, the web-based management interface fails to properly neutralize script-related HTML tags in user-supplied input fields. This insufficient input validation allows an authenticated remote attacker with low privileges—specifically those with valid credentials permitting vKVM access—to inject malicious script code into the interface. When a legitimate user accesses the affected interface, the injected script executes in their browser context, potentially exposing sensitive browser-based information or enabling further attacks such as session hijacking or unauthorized actions within the management interface. The vulnerability requires authentication and user interaction (the victim must access the maliciously crafted interface), but the attacker privileges needed are relatively low, increasing the risk in environments where multiple users have vKVM access. The vulnerability affects a broad set of Cisco UCS Manager versions, indicating a wide deployment footprint. The CVSS v3.1 base score is 5.4 (medium), reflecting network attack vector, low attack complexity, low privileges required, and user interaction needed, with partial confidentiality and integrity impact but no availability impact. No known exploits are currently reported in the wild, but the potential for exploitation exists given the nature of the vulnerability and the critical role of UCS in data center infrastructure management.

For European organizations, the impact of this vulnerability can be significant due to the widespread use of Cisco UCS infrastructure in enterprise data centers, cloud providers, and critical industries such as finance, telecommunications, and government. Exploitation could lead to unauthorized disclosure of sensitive management interface data, including session tokens or configuration details, potentially enabling lateral movement or privilege escalation within the network. Since the vulnerability affects the management plane of UCS systems, successful attacks could undermine the integrity of server management operations, risking misconfiguration or disruption of critical services. The requirement for valid credentials somewhat limits the attack surface, but insider threats or compromised accounts could be leveraged. Additionally, the stored XSS nature means persistent malicious code could affect multiple users over time, increasing risk. European organizations with strict data protection regulations (e.g., GDPR) must consider the confidentiality impact seriously, as leakage of sensitive information through browser-based attacks could lead to compliance violations and reputational damage.

To mitigate this vulnerability effectively, European organizations should: 1) Immediately identify and inventory all Cisco UCS Manager and IMC instances in their environment, noting versions to assess exposure. 2) Apply Cisco-released patches or updates as soon as they become available, prioritizing environments with multiple vKVM users. 3) Restrict vKVM access privileges strictly on a need-to-use basis, minimizing the number of users with such permissions. 4) Implement multi-factor authentication (MFA) for management interfaces to reduce the risk of credential compromise. 5) Monitor management interface logs for unusual input patterns or repeated failed attempts that could indicate exploitation attempts. 6) Educate administrators and users with vKVM access about the risks of stored XSS and encourage cautious behavior when interacting with management interfaces. 7) Where possible, isolate management interfaces from general network access using network segmentation and VPNs to limit exposure. 8) Employ web application firewalls (WAFs) or intrusion detection systems (IDS) tuned to detect and block XSS payloads targeting management interfaces. These measures, combined, reduce the likelihood of successful exploitation and limit potential damage.