Cisco has recently disclosed a critical zero-day vulnerability, designated as CVE-2025-20352, within its widely utilized IOS and IOS XE software platforms. This flaw resides in the Simple Network Management Protocol (SNMP) subsystem and has been confirmed to be actively exploited in real-world scenarios. The vulnerability was initially identified during an investigation by Cisco’s Technical Assistance Center (TAC).
Understanding the Vulnerability
The core issue stems from a stack-based buffer overflow (CWE-121) within the SNMP subsystem of both Cisco IOS and IOS XE software. An attacker can exploit this flaw by transmitting a specially crafted SNMP packet over IPv4 or IPv6 networks to a susceptible device. Notably, all versions of SNMP (v1, v2c, and v3) are vulnerable to this exploit.
Potential Impact Based on Attacker Privileges
The severity of the exploit varies depending on the attacker’s level of access:
– Low-Privileged Attacker: An authenticated remote attacker with minimal privileges can cause the affected device to reload, resulting in a denial-of-service (DoS) condition. This requires access to an SNMPv2c read-only community string or valid SNMPv3 user credentials.
– High-Privileged Attacker: An attacker possessing administrative or privilege level 15 credentials can execute arbitrary code as the ‘root’ user on devices running IOS XE, thereby gaining full control over the system.
Active Exploitation and Affected Devices
Cisco’s Product Security Incident Response Team (PSIRT) has confirmed instances of this vulnerability being exploited in the wild. Attackers have been observed leveraging this flaw after initially compromising local administrator credentials, indicating a sophisticated, multi-stage attack strategy.
The vulnerability affects a broad spectrum of Cisco devices running vulnerable versions of IOS and IOS XE software with SNMP enabled. Specific products mentioned include the Meraki MS390 and Cisco Catalyst 9300 Series Switches.
Mitigation and Remediation Strategies
Cisco has released software updates to address this vulnerability and strongly recommends that all customers upgrade to a patched software release to fully remediate the issue. The advisory, identified as ‘cisco-sa-snmp-x4LPhte,’ clarifies that there are no workarounds available.
For organizations unable to immediately apply the updates, Cisco has provided a mitigation technique. Administrators can configure an SNMP view to exclude the affected object IDs (OIDs), preventing the vulnerable code path from being triggered. However, Cisco cautions that this mitigation may disrupt network management functionalities, such as device discovery and hardware inventory monitoring. As a general security measure, Cisco also advises restricting SNMP access to only trusted users.
Broader Implications and Recommendations
This incident underscores the critical importance of robust credential management and timely software updates. Organizations are urged to review their network configurations, ensure that SNMP access is restricted to trusted users, and apply the necessary patches without delay. Regular monitoring and auditing of network devices for unusual activity can also help in early detection and mitigation of potential exploits.
Conclusion
The disclosure of CVE-2025-20352 highlights the ever-present threats to network infrastructure and the necessity for proactive security measures. By understanding the nature of this vulnerability and implementing the recommended remediation strategies, organizations can safeguard their networks against potential attacks.
