CVE-2025-20327 is a high-severity vulnerability affecting multiple versions of Cisco IOS software, specifically versions 15.2(6)E2 through 15.2(8)E5 and related subversions. The vulnerability exists in the web user interface (UI) component of Cisco IOS, where improper validation of input types allows an authenticated remote attacker with low privileges to send a specially crafted HTTP request containing a malicious URL. This malformed input triggers a flaw in the input validation logic, causing the affected device to reload unexpectedly. The forced reload results in a denial of service (DoS) condition, disrupting network operations. The vulnerability requires the attacker to be authenticated but does not require user interaction beyond sending the crafted HTTP request. The CVSS v3.1 base score is 7.7, reflecting a high severity due to the network attack vector, low attack complexity, required privileges, and the impact limited to availability (no confidentiality or integrity impact). The scope is changed, indicating that the vulnerability affects components beyond the initially vulnerable component, potentially impacting the entire device's operation. No known exploits are currently reported in the wild, and no patches or mitigation links have been provided yet. However, the broad range of affected IOS versions indicates that many Cisco routers and network devices could be vulnerable, especially those using the web UI for management.

For European organizations, this vulnerability poses a significant risk to network infrastructure stability and availability. Cisco IOS is widely deployed across enterprise, service provider, and governmental networks in Europe, forming the backbone of critical communications and data routing. A successful exploit could cause routers or switches to reload unexpectedly, leading to network outages, degraded service, and potential disruption of business-critical applications. This is particularly impactful for sectors relying on continuous network uptime such as finance, healthcare, telecommunications, and public administration. The requirement for authentication limits exploitation to insiders or attackers who have obtained valid credentials, but the low privilege requirement means even less-privileged users could trigger the DoS. The resulting downtime could affect data center connectivity, branch office communications, and internet access, potentially causing cascading operational impacts and financial losses. Additionally, the vulnerability could be leveraged as part of a broader attack campaign to disrupt services or as a diversion tactic during more sophisticated intrusions.

1. Immediate mitigation should focus on restricting access to the Cisco IOS web UI management interface to trusted administrators only, ideally via secure management VLANs or out-of-band management networks. 2. Implement strong authentication controls, including multi-factor authentication (MFA), to reduce the risk of credential compromise. 3. Monitor network devices for unusual reloads or HTTP request patterns targeting the web UI, and enable logging to detect potential exploitation attempts. 4. Apply network segmentation to isolate critical infrastructure devices from general user networks to limit exposure. 5. Since no patches are currently listed, maintain close coordination with Cisco for timely release and deployment of security updates addressing this vulnerability. 6. Consider disabling the web UI management interface if not strictly necessary, switching to more secure management protocols such as SSH or dedicated management tools. 7. Conduct regular vulnerability assessments and penetration tests focusing on network device management interfaces to proactively identify and remediate weaknesses. 8. Educate network administrators about this vulnerability and the importance of safeguarding credentials and access to management interfaces.