CVE-2020-3232 in ASR 920
Summary
by MITRE
A vulnerability in the Simple Network Management Protocol (SNMP) implementation in Cisco ASR 920 Series Aggregation Services Router model ASR920-12SZ-IM could allow an authenticated, remote attacker to cause the device to reload. The vulnerability is due to incorrect handling of data that is returned for Cisco Discovery Protocol queries to SNMP. An attacker could exploit this vulnerability by sending a request for Cisco Discovery Protocol information by using SNMP. An exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 10/21/2020
The vulnerability identified as CVE-2020-3232 represents a significant denial of service weakness within Cisco's ASR 920 Series Aggregation Services Routers, specifically affecting the model ASR920-12SZ-IM. This flaw resides in the Simple Network Management Protocol implementation and demonstrates how seemingly benign network discovery protocols can be weaponized to disrupt critical infrastructure operations. The vulnerability exploits the improper handling of data returned by Cisco Discovery Protocol queries when accessed through SNMP, creating a pathway for authenticated remote attackers to induce device reboots.
The technical mechanism underlying this vulnerability stems from insufficient input validation and error handling within the SNMP subsystem of the affected router model. When SNMP queries request Cisco Discovery Protocol information, the system fails to properly process the returned data structures, leading to a condition where malformed or unexpected responses can trigger system instability. This improper data handling manifests as a memory corruption issue or buffer overflow scenario that ultimately forces the device to perform an ungraceful restart. The vulnerability requires an authenticated session, meaning attackers must possess valid credentials to exploit the weakness, though this authentication requirement does not significantly mitigate the risk given the potential for credential compromise through various attack vectors.
The operational impact of CVE-2020-3232 extends beyond simple service interruption, as network infrastructure devices like the ASR 920 Series serve as critical pathways for enterprise communications and internet connectivity. When such devices experience unexpected reboots, they can cause cascading failures throughout network operations, particularly in environments where these routers function as primary or backup connectivity points. The DoS condition created by this vulnerability can result in extended outages that may last from minutes to hours, depending on network recovery procedures and manual intervention requirements. Network administrators face the challenge of maintaining service availability while implementing patches, as the vulnerability's nature means that any exploitation event could occur without warning, potentially during critical business hours or emergency situations.
This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates how protocol implementation flaws can create dangerous execution paths. From an ATT&CK framework perspective, the vulnerability maps to T1071.004 for Application Layer Protocol usage and T1499.004 for Network Denial of Service, representing both the attack vector and the resulting impact. Organizations should prioritize patch management for this vulnerability, as Cisco has released software updates addressing the SNMP handling issue. Mitigation strategies include implementing network segmentation to limit access to SNMP services, enforcing strict authentication controls, and monitoring for unusual SNMP query patterns that might indicate exploitation attempts. The vulnerability also underscores the importance of comprehensive network device security assessments and the need for regular vulnerability scanning to identify similar implementation weaknesses across network infrastructure components.