CVE-2025-20248 is a cryptographic signature verification bypass vulnerability in Cisco IOS XR Software's installation process. The vulnerability stems from incomplete validation of files within .iso images used for software installation. An attacker with root-system privileges on the device can modify the contents of the .iso image to include unsigned or malicious software components. When the modified .iso is installed and activated, the device accepts and runs the unsigned software, bypassing the intended cryptographic signature checks designed to ensure software integrity and authenticity. This flaw impacts a broad range of Cisco IOS XR versions, from 6.5.x through 7.x and 24.x releases, indicating a long-standing issue across multiple releases. The vulnerability requires local authenticated access with high privileges, meaning remote exploitation is not feasible without prior compromise. The CVSS v3.1 base score is 6.0 (medium severity), reflecting the high impact on confidentiality and integrity but limited attack vector (local) and requirement for high privileges. No public exploits or active exploitation have been reported yet. The vulnerability could allow attackers to load malicious code, potentially leading to unauthorized data access, manipulation, or persistence on critical network infrastructure devices running Cisco IOS XR.

The vulnerability poses a significant risk to organizations relying on Cisco IOS XR Software for routing and network infrastructure, especially large enterprises and service providers. If exploited, attackers with root access can load unsigned and potentially malicious software, compromising device confidentiality and integrity. This could lead to unauthorized data interception, network manipulation, or persistent backdoors within critical network devices. Although availability impact is not directly indicated, compromised devices could be leveraged for further attacks or cause network disruptions indirectly. The requirement for root privileges limits the attack surface but elevates the risk if internal threat actors or attackers who have already gained privileged access exploit this flaw. Given Cisco IOS XR's widespread deployment in critical backbone and edge networks globally, the vulnerability could have cascading effects on network security and trustworthiness.

Organizations should immediately identify and inventory all Cisco IOS XR devices running affected versions. Cisco is expected to release patches or updates addressing this vulnerability; applying these updates promptly is critical. Until patches are available, restrict root-system access strictly to trusted administrators and implement robust internal access controls and monitoring to detect unauthorized privilege escalations. Employ multi-factor authentication and limit the number of users with root privileges. Validate all software images before installation and consider using out-of-band verification methods to ensure image integrity. Network segmentation and strict change management policies can reduce the risk of unauthorized image installation. Regularly audit device configurations and logs for signs of tampering or unauthorized software installations. Finally, maintain up-to-date backups and incident response plans tailored to network infrastructure compromise scenarios.