CVE-2026-20123 is a medium-severity open redirect vulnerability found in the web-based management interfaces of Cisco Evolved Programmable Network Manager (EPNM) and Cisco Prime Infrastructure. The flaw stems from improper input validation of URL parameters within HTTP requests, allowing an unauthenticated remote attacker to craft malicious URLs that redirect legitimate users to untrusted, potentially harmful websites. The attacker can intercept and modify HTTP requests or lure users into clicking specially crafted links. This vulnerability does not require authentication but does require user interaction to trigger the redirect. The vulnerability affects multiple versions of Cisco EPNM, including 7.1.0 through 8.1.0 and their minor updates. Although the vulnerability does not directly impact confidentiality or availability, it can be leveraged in phishing campaigns or to deliver malware by redirecting users to malicious domains. No known exploits are currently reported in the wild. The CVSS v3.1 base score is 4.3, indicating a medium severity level due to the lack of direct system compromise and the need for user interaction. Cisco has not yet published patches or mitigation details at the time of this report.

For European organizations, this vulnerability poses a moderate risk primarily through social engineering and phishing attacks. Since Cisco EPNM is widely used in telecommunications and large enterprise network management, attackers could exploit this flaw to redirect network administrators or users to malicious sites, potentially leading to credential theft or malware infection. The indirect nature of the threat means it could facilitate further attacks rather than cause immediate system compromise. Organizations relying on Cisco EPNM for critical network infrastructure management could face operational risks if attackers successfully leverage this vulnerability to gain footholds or disrupt trust in management portals. The impact is heightened in sectors with stringent regulatory requirements for data protection and network integrity, such as finance, healthcare, and government institutions across Europe.

Organizations should immediately review and restrict access to Cisco EPNM web interfaces, especially from untrusted networks. Implement strict input validation and URL filtering on web gateways and proxies to detect and block suspicious redirect attempts. Educate users and administrators about the risks of clicking unsolicited or suspicious links, particularly those purporting to be from network management tools. Monitor network traffic for unusual redirect patterns and employ web security solutions capable of detecting open redirect exploitation. Cisco customers should track vendor advisories closely and apply patches or updates as soon as they become available. Additionally, consider implementing multi-factor authentication and session timeout policies to reduce the risk of session hijacking facilitated by phishing. Network segmentation can limit exposure of the management interface to only trusted personnel and systems.