CVE-2025-20169 in IOS
Summary
by MITRE • 02/05/2025
A vulnerability in the SNMP subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to cause a DoS condition on an affected device.
This vulnerability is due to improper error handling when parsing SNMP requests. An attacker could exploit this vulnerability by sending a crafted SNMP request to an affected device. A successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition. This vulnerability affects SNMP versions 1, 2c, and 3. To exploit this vulnerability through SNMP v2c or earlier, the attacker must know a valid read-write or read-only SNMP community string for the affected system. To exploit this vulnerability through SNMP v3, the attacker must have valid SNMP user credentials for the affected system.
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Analysis
by VulDB Data Team • 10/31/2025
This vulnerability represents a critical denial of service weakness within Cisco's network infrastructure software affecting both IOS and IOS XE platforms. The flaw manifests in the SNMP subsystem's error handling mechanisms, specifically when processing incoming SNMP requests from remote attackers. The vulnerability impacts all three major SNMP versions including v1, v2c, and v3, creating a broad attack surface that network administrators must address. The root cause stems from inadequate input validation and error management within the SNMP processing pipeline, where malformed requests trigger unexpected system behavior rather than graceful error recovery.
The technical exploitation of this vulnerability requires an authenticated attacker who can successfully establish communication with the target device through SNMP protocols. For SNMP versions 1 and 2c, attackers must possess valid community strings with read-write or read-only privileges to craft malicious requests that trigger the DoS condition. In the case of SNMP v3, attackers need valid user credentials including username and authentication keys, making the attack more complex but still feasible for those who have gained access to legitimate SNMP accounts. The vulnerability's design flaw lies in how the system handles malformed SNMP packets during parsing operations, leading to unexpected system reloads that disrupt network services and create operational downtime.
From an operational impact perspective, this vulnerability poses significant risks to network availability and reliability. When exploited successfully, the device undergoes unexpected reload operations that can last several minutes, depending on the device configuration and network complexity. During this downtime, network monitoring and management capabilities are temporarily unavailable, potentially masking other security incidents or network issues. The vulnerability affects critical network infrastructure components including routers, switches, and network management systems that rely on SNMP for operational monitoring and configuration management. This disruption can cascade through network operations, particularly in environments where SNMP is used for automated network management, performance monitoring, and security event correlation.
Network security professionals should consider this vulnerability in relation to the CWE-20 weakness category, which specifically addresses "Improper Input Validation" and the broader ATT&CK framework's T1499.1 technique for "Network Denial of Service" targeting network infrastructure components. Mitigation strategies should include implementing network segmentation to limit SNMP access to trusted management stations, enforcing strict access control lists that restrict SNMP communication to authorized networks, and applying Cisco's recommended security patches and firmware updates. Organizations should also consider disabling SNMPv1 and v2c protocols in favor of SNMPv3 when possible, as the latter provides better authentication and encryption mechanisms that reduce the attack surface. Regular monitoring of SNMP traffic and implementation of intrusion detection systems can help identify potential exploitation attempts before they succeed in causing service disruption.