CVE-2025-20352 is a stack-based buffer overflow vulnerability located in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS and IOS XE software. The flaw arises from improper handling of crafted SNMP packets, which can overflow a stack buffer leading to memory corruption. The vulnerability can be exploited remotely over IPv4 or IPv6 networks by sending malicious SNMP packets. For low-privilege authenticated users possessing SNMPv2c or earlier read-only community strings or valid SNMPv3 credentials, exploitation results in a denial of service (DoS) condition, causing the device to crash or reboot, thus disrupting network availability. For high-privilege attackers with administrative or privilege 15 credentials, the vulnerability allows arbitrary code execution with root privileges on IOS XE devices, enabling full device compromise. The vulnerability affects a broad range of Cisco IOS versions, including many 12.x, 15.x, and 15.6.x releases, indicating widespread exposure. Exploitation requires authentication but no user interaction, and the vulnerability has a CVSS 3.1 base score of 7.7, reflecting high severity due to the potential for DoS and remote code execution. No known public exploits are reported yet, but the extensive affected versions and critical impact necessitate urgent remediation. The vulnerability undermines device integrity and availability, threatening the stability of network infrastructure relying on Cisco IOS devices.

For European organizations, this vulnerability poses significant risks to network infrastructure stability and security. Cisco IOS and IOS XE devices are widely deployed in enterprise networks, telecommunications, and critical infrastructure across Europe. A successful low-privilege exploit can cause denial of service, leading to network outages, degraded service, and operational disruptions. More severe is the potential for high-privilege attackers to execute arbitrary code as root, which could allow attackers to install persistent malware, intercept or manipulate network traffic, and pivot to other internal systems. This could result in data breaches, espionage, or sabotage of critical communications. The broad range of affected IOS versions means many organizations may have vulnerable devices in production. Given the critical role of Cisco devices in European telecom operators and large enterprises, the impact could extend to national infrastructure and essential services. The requirement for authentication limits exposure but does not eliminate risk, especially if SNMP credentials are weak, reused, or compromised. The vulnerability could be leveraged in targeted attacks against high-value networks or supply chain attacks affecting multiple organizations.

European organizations should immediately inventory Cisco IOS and IOS XE devices to identify affected versions. They should apply Cisco's security patches or software updates that address CVE-2025-20352 as soon as they become available. Until patches are applied, organizations should restrict SNMP access strictly to trusted management hosts using access control lists (ACLs) and network segmentation to minimize exposure. Disable SNMPv1 and SNMPv2c protocols if not required, and prefer SNMPv3 with strong authentication and encryption. Rotate SNMP community strings and user credentials regularly, ensuring they are complex and unique. Monitor network traffic for anomalous SNMP packets indicative of exploitation attempts. Employ intrusion detection/prevention systems (IDS/IPS) with updated signatures to detect crafted SNMP packets targeting this vulnerability. Conduct regular audits of device configurations and credentials to prevent privilege escalation. For high-security environments, consider temporarily disabling SNMP services if feasible. Finally, maintain robust incident response plans to quickly address any signs of compromise related to this vulnerability.