CVE-2025-20171 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 • 07/03/2025
This vulnerability represents a critical denial-of-service weakness within Cisco's network infrastructure software, specifically targeting the SNMP subsystem that forms a fundamental component of network monitoring and management operations. The flaw exists in both Cisco IOS Software and Cisco IOS XE Software, affecting a broad range of network devices including routers, switches, and other network appliances that rely on SNMP for operational management. The vulnerability stems from inadequate error handling mechanisms during SNMP request processing, creating a condition where malformed or specially crafted requests can trigger unexpected system behavior. This represents a classic example of insufficient input validation and error handling, which falls under CWE-248, where an exception is thrown but not properly caught, leading to application instability. The impact extends across all SNMP versions 1, 2c, and 3, demonstrating the widespread nature of this vulnerability within the SNMP ecosystem.
The exploitation mechanism involves an authenticated remote attacker who can craft specific SNMP requests to trigger the device reload condition, effectively creating a denial-of-service scenario that disrupts network operations. This attack vector aligns with ATT&CK technique T1499.001, which describes network disruption through service interruption, and T1566.001, which covers social engineering via spearphishing attachments or links. For SNMP versions 1 and 2c, the attack requires knowledge of valid community strings, which function as passwords for SNMP access, making this vulnerability more accessible to attackers who have already gained some level of network access or have obtained legitimate credentials through other means. The requirement for valid SNMP v3 credentials demonstrates that this vulnerability affects both unauthenticated and authenticated attack scenarios, with the latter being more severe as SNMP v3 provides authentication and encryption. The device reloading process represents a complete service interruption that can take network systems offline for extended periods, potentially causing cascading failures in network infrastructure that relies on these devices.
The operational impact of this vulnerability extends beyond simple service interruption to potentially compromise network stability and availability, especially in mission-critical environments where network uptime is essential. Network administrators may experience unexpected outages that could affect business operations, service delivery, and customer satisfaction. The vulnerability's presence in both IOS and IOS XE software indicates that it affects a significant portion of Cisco's installed base, potentially impacting thousands of network devices worldwide. The DoS condition created by the device reload can be particularly problematic in redundant network architectures where the failure of one device could trigger cascading failures or force network traffic through alternative paths that may not be properly configured. This vulnerability also represents a potential stepping stone for more sophisticated attacks, as network administrators may be distracted by the DoS conditions while more serious attacks occur. The fact that this vulnerability affects all SNMP versions suggests that network administrators may not be able to avoid it by simply disabling certain SNMP versions, requiring more comprehensive mitigation approaches.
Mitigation strategies should focus on immediate patching of affected devices, which aligns with the ATT&CK technique T1543.003 for persistence mechanisms and T1595.001 for reconnaissance. Network administrators should implement SNMP access controls and community string management, ensuring that only authorized users have access to SNMP functionality. The implementation of SNMPv3 with strong authentication and encryption should be prioritized over older versions that lack proper security mechanisms. Network segmentation and access control lists should be configured to limit SNMP access to trusted network segments, reducing the attack surface for remote exploitation. Additionally, monitoring systems should be enhanced to detect unusual SNMP traffic patterns that might indicate exploitation attempts. Regular security audits and vulnerability assessments should be conducted to identify and remediate similar issues in other network subsystems. The vulnerability's nature suggests that implementing robust error handling mechanisms and input validation in network software development processes could prevent similar issues in the future, aligning with security best practices outlined in NIST SP 800-53 and ISO 27001 frameworks.