CVE-2022-20924: Cisco ASA Software SNMP DoS Vulnerability

CVE-2022-20924 Overview

A vulnerability in the Simple Network Management Protocol (SNMP) feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

This vulnerability is due to insufficient input validation in the SNMP feature. 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 affected device to reload, resulting in a DoS condition that disrupts network security operations.

Critical Impact

Authenticated attackers can remotely crash Cisco ASA and FTD firewalls through malformed SNMP requests, potentially disrupting critical network security infrastructure and leaving networks temporarily unprotected.

Affected Products

• Cisco Adaptive Security Appliance (ASA) Software versions 9.14.x through 9.18.1
• Cisco Firepower Threat Defense (FTD) Software versions 6.6.x through 7.2.0.1
• Multiple point releases across ASA 9.14, 9.15, 9.16, 9.17, and 9.18 branches

Discovery Timeline

• November 15, 2022 - CVE-2022-20924 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-20924

Vulnerability Analysis

This denial of service vulnerability affects the SNMP subsystem within Cisco's security appliance platforms. The vulnerability allows an authenticated remote attacker to trigger a device reload by exploiting improper input handling in the SNMP protocol implementation. When successfully exploited, the target firewall or threat defense appliance will crash and restart, causing a temporary but significant disruption to network security services.

The impact is particularly concerning for enterprise environments where Cisco ASA or FTD devices serve as primary perimeter security controls. During the reload period, network traffic may be disrupted or left unprotected depending on the deployment architecture and failover configuration.

Root Cause

The vulnerability stems from insufficient input validation (CWE-20) and improper handling of exceptional conditions (CWE-703) within the SNMP feature implementation. When the SNMP subsystem processes specially crafted requests, it fails to properly validate or sanitize input data, leading to an unhandled exception that causes the device to reload.

The dual CWE classification indicates that the vulnerability involves both missing input validation checks and inadequate exception handling mechanisms that should prevent the device from crashing even when encountering malformed data.

Attack Vector

The attack is network-based and requires the attacker to have valid SNMP credentials (authentication required). The attacker must craft a malicious SNMP request containing specific malformed data and send it to the management interface of the target device where SNMP is enabled.

The exploitation flow involves:

1. The attacker identifies a vulnerable Cisco ASA or FTD device with SNMP enabled
2. Using valid SNMP community strings or SNMPv3 credentials, the attacker sends a specially crafted SNMP request
3. The device's SNMP subsystem fails to properly validate the malformed input
4. The improper exception handling causes the device to crash and reload
5. Network security services are temporarily disrupted during the reload process

For detailed technical information about this vulnerability, refer to the Cisco Security Advisory.

Detection Methods for CVE-2022-20924

Indicators of Compromise

• Unexpected device reloads or crashes on Cisco ASA or FTD appliances with SNMP enabled
• Crash dump files or syslog entries indicating SNMP-related failures
• Anomalous SNMP traffic patterns from unexpected sources
• Multiple sequential device restarts in short time periods

Detection Strategies

• Monitor SNMP traffic for malformed or unusually structured requests targeting ASA/FTD devices
• Configure syslog alerting for unexpected device reload events
• Implement network-based intrusion detection signatures for SNMP anomalies
• Review authentication logs for SNMP access attempts from unauthorized sources

Monitoring Recommendations

• Enable detailed logging on SNMP subsystem activities on affected devices
• Deploy network traffic analysis to baseline normal SNMP communication patterns
• Configure SNMP management station alerts for device availability monitoring
• Implement centralized log aggregation to correlate SNMP-related events across multiple devices

How to Mitigate CVE-2022-20924

Immediate Actions Required

• Review and update Cisco ASA and FTD software to patched versions as outlined in the Cisco Security Advisory
• Restrict SNMP access to trusted management networks and IP addresses only
• Audit SNMP community strings and SNMPv3 credentials to ensure strong authentication
• Consider disabling SNMP if not required for operational monitoring

Patch Information

Cisco has released software updates that address this vulnerability. Organizations should consult the Cisco Security Advisory to determine the appropriate fixed software release for their specific ASA or FTD version. The advisory provides detailed version mapping to identify the minimum patched release for each affected software branch.

Workarounds

• Disable SNMP entirely if the feature is not operationally required
• Implement strict access control lists (ACLs) to limit SNMP access to authorized management stations only
• Use SNMPv3 with strong authentication and encryption rather than SNMPv1/v2c
• Deploy the device behind additional network segmentation to limit exposure

# Example: Restrict SNMP access to specific management hosts
# Cisco ASA configuration
snmp-server host management 10.0.0.100 community <strong-community>
snmp-server host management 10.0.0.101 community <strong-community>

# Disable SNMP if not required
no snmp-server enable