CVE-2025-20173 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 • 03/13/2025
This vulnerability resides within the SNMP subsystem of Cisco IOS and IOS XE software implementations, representing a critical flaw that undermines network device stability and availability. The issue manifests as improper error handling during SNMP request processing, creating a condition where maliciously crafted requests can trigger unintended system behavior. The vulnerability impacts all three major SNMP versions, indicating a fundamental flaw in the software's request parsing logic that affects both legacy and modern SNMP implementations. Network administrators must understand that this weakness operates at the protocol level, where legitimate network management traffic becomes a potential vector for deliberate disruption. The affected software spans multiple Cisco product lines, making this vulnerability particularly concerning for organizations relying on Cisco networking infrastructure for critical operations. This type of vulnerability directly violates the principle of robust error handling that should prevent malformed input from causing system instability.
The technical exploitation mechanism involves sending specifically crafted SNMP requests that trigger the flawed error handling routine within the IOS software. When processing these malformed requests, the system fails to properly validate or sanitize incoming data, leading to a critical failure state that results in unexpected device reloads. The vulnerability's impact is amplified by the fact that it requires minimal privileges for exploitation, as attackers only need valid SNMP credentials corresponding to the targeted version. For SNMP v2c and earlier versions, knowledge of a valid community string provides sufficient access to initiate the attack, while SNMP v3 requires more sophisticated credentials but still maintains the same fundamental flaw. This exploitation pattern aligns with common attack vectors identified in the ATT&CK framework under the 'Execution' and 'Resource Hijacking' domains, where adversaries leverage legitimate system interfaces to cause system instability. The error handling failure creates a path where normal protocol processing transitions into a critical failure state, demonstrating poor defensive programming practices that violate established security principles.
The operational impact of this vulnerability extends beyond simple denial of service, as it can disrupt critical network operations and potentially cause cascading failures throughout network infrastructure. When devices unexpectedly reload, network services experience interruptions that can affect multiple systems depending on the device's role within the network topology. The vulnerability's presence in both SNMP v1 and v3 implementations means that organizations cannot avoid exposure by simply disabling older protocols, as the flaw exists across the entire SNMP protocol stack. Network monitoring systems may struggle to distinguish between legitimate device reboots and malicious exploitation attempts, complicating incident response efforts. The vulnerability's exploitation requires minimal technical skill and resources, making it attractive to threat actors seeking to disrupt network operations. Organizations with extensive SNMP-based monitoring and management systems face particular risk, as the attack can be executed without requiring advanced penetration testing skills or specialized tools. This characteristic places the vulnerability in the ATT&CK matrix under 'Denial of Service' techniques where adversaries target system availability through legitimate protocol interfaces.
Mitigation strategies should focus on immediate network segmentation and access control measures to limit SNMP exposure to trusted networks only. Organizations must implement strict SNMP community string management and regularly audit access permissions to reduce the attack surface. Network administrators should consider disabling SNMP v1 and v2c where possible, as these versions are more susceptible to exploitation due to their less secure authentication mechanisms. The implementation of SNMPv3 with strong authentication and encryption protocols provides better protection against this vulnerability, though the underlying flaw remains present in the software parsing logic. Regular software updates and patches from Cisco should be prioritized to address the root cause of the improper error handling. Network monitoring solutions should be enhanced to detect unusual reload patterns and SNMP traffic anomalies that may indicate exploitation attempts. Security teams should also implement network access control lists to restrict SNMP traffic to known management systems only, reducing the opportunity for unauthorized exploitation. The vulnerability's nature suggests that defensive measures should include input validation and robust error handling mechanisms that prevent malformed requests from triggering system failures, aligning with CWE guidelines for secure coding practices in protocol implementations.