CVE-2025-20172 in IOS
Summary
by MITRE • 02/05/2025
A vulnerability in the SNMP subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR 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. For Cisco IOS and IOS XE Software, a successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition. For Cisco IOS XR Software, a successful exploit could allow the attacker to cause the SNMP process to restart, resulting in an interrupted SNMP response from an affected device. Devices that are running Cisco IOS XR Software will not reload. 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 • 03/13/2025
This vulnerability represents a critical denial of service weakness within Cisco's network infrastructure software ecosystems affecting multiple IOS variants. The flaw exists within the SNMP subsystem where inadequate error handling mechanisms fail to properly process malformed or crafted SNMP requests. This vulnerability falls under the CWE-248 category of "Uncaught Exception" and demonstrates how improper input validation can lead to system instability. The attack vector requires authentication, making it less accessible than fully unauthenticated exploits but still concerning given the potential for network disruption. The vulnerability impacts three major Cisco software platforms including IOS Software, IOS XE Software, and IOS XR Software, indicating a widespread issue across the company's networking portfolio.
The technical exploitation mechanism operates through the parsing of SNMP requests where the system fails to properly handle malformed input data. When an attacker submits a specially crafted SNMP packet, the system's error handling routines cannot gracefully manage the unexpected input, leading to system instability. For Cisco IOS and IOS XE platforms, this results in unexpected device reloads that effectively deny service to legitimate network users. The IOS XR platform experiences a different but equally disruptive outcome where the SNMP process restarts, causing temporary interruption of SNMP responses without full device reload. This differential impact reflects the varying architectural approaches between the software variants, though both represent significant operational risks. The vulnerability specifically affects all SNMP versions 1, 2c, and 3, making it particularly dangerous as it encompasses the majority of SNMP implementations in enterprise networks.
The operational impact of this vulnerability extends beyond simple network disruption to potentially compromise network monitoring capabilities and overall system reliability. Network administrators rely heavily on SNMP for device monitoring, performance tracking, and configuration management, making any SNMP-related disruption particularly problematic. The requirement for valid SNMP credentials adds a layer of complexity to exploitation but also highlights the importance of proper credential management and access control. In enterprise environments where SNMP is widely deployed, this vulnerability could be exploited by insiders with appropriate privileges or by external attackers who have obtained valid SNMP community strings or user credentials. The attack could be particularly damaging in mission-critical environments where network uptime is essential, as it directly impacts the availability of network management functions.
Mitigation strategies should focus on multiple defensive layers including immediate patch application for all affected software versions, proper SNMP credential management, and network segmentation to limit potential attack surfaces. Organizations should implement strict SNMP access controls, regularly audit SNMP community strings, and consider disabling unnecessary SNMP versions where possible. The vulnerability demonstrates the importance of robust error handling in network infrastructure software and aligns with ATT&CK technique T1499.004 for network denial of service attacks. Network administrators should also implement monitoring solutions to detect unusual SNMP traffic patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should include SNMP subsystem evaluation to identify potential exposure points and ensure proper configuration of SNMP services across all network devices.