CVE-2020-3254 Overview
Multiple vulnerabilities in the Media Gateway Control Protocol (MGCP) inspection feature of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerabilities are due to inefficient memory management. An attacker could exploit these vulnerabilities by sending crafted MGCP packets through an affected device. An exploit could allow the attacker to cause memory exhaustion resulting in a restart of an affected device, causing a DoS condition for traffic traversing the device.
Critical Impact
Unauthenticated remote attackers can cause memory exhaustion and device restart, disrupting all traffic traversing the affected firewall or security appliance.
Affected Products
- Cisco Adaptive Security Appliance (ASA) Software
- Cisco Firepower Threat Defense (FTD) Software
- Cisco ASA 5500-X Series (5505, 5510, 5512-X, 5515-X, 5520, 5525-X, 5540, 5545-X, 5550, 5555-X, 5580, 5585-X)
Discovery Timeline
- May 6, 2020 - CVE-2020-3254 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2020-3254
Vulnerability Analysis
This vulnerability resides in the MGCP inspection functionality of Cisco ASA and FTD software. MGCP is a signaling and call control protocol used in Voice over IP (VoIP) deployments, particularly for communication between Media Gateways and Media Gateway Controllers. When MGCP inspection is enabled on affected devices, the software fails to properly manage memory when processing specially crafted MGCP packets.
The inefficient memory management (CWE-400: Uncontrolled Resource Consumption) allows an attacker to trigger memory exhaustion by sending a sequence of malicious MGCP packets through the device. Because no authentication is required and the attack can be conducted remotely over the network, any device with MGCP inspection enabled and reachable via network is potentially vulnerable.
Root Cause
The root cause of this vulnerability is inefficient memory management within the MGCP inspection engine. When processing certain MGCP packets, the software fails to properly release allocated memory resources, leading to a memory leak condition. Over time, or through a targeted attack involving many malicious packets, memory resources become exhausted, forcing the device to restart to recover normal operation.
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:
- Identifying a Cisco ASA or FTD device with MGCP inspection enabled
- Crafting malicious MGCP packets designed to trigger the memory management flaw
- Sending these packets through the affected device
- Causing progressive memory exhaustion until the device restarts
The vulnerability can be exploited remotely over the network without requiring any privileges on the target device. The attack results in a denial of service condition affecting all traffic traversing the security appliance. Detailed technical information about the specific packet structures involved can be found in the Cisco Security Advisory.
Detection Methods for CVE-2020-3254
Indicators of Compromise
- Unexpected device restarts or reboots without administrative action
- Progressive increase in memory utilization on ASA or FTD devices
- Unusual volume of MGCP traffic (typically UDP port 2427) traversing the device
- Memory exhaustion warnings or errors in system logs
Detection Strategies
- Monitor ASA/FTD memory utilization for abnormal patterns or gradual increases that don't correlate with legitimate traffic growth
- Implement network traffic analysis to detect anomalous MGCP packet volumes or malformed MGCP traffic
- Configure SNMP traps or syslog alerts for memory threshold warnings on affected devices
- Review system logs for unexpected device reloads or memory-related error messages
Monitoring Recommendations
- Enable logging for MGCP inspection events and review logs regularly for suspicious activity
- Set up automated alerting for memory utilization thresholds (e.g., above 80%)
- Monitor for unexpected device availability changes using network management tools
- Implement baseline traffic analysis to identify unusual MGCP traffic patterns
How to Mitigate CVE-2020-3254
Immediate Actions Required
- Verify if MGCP inspection is enabled on your Cisco ASA or FTD devices using show service-policy
- Apply Cisco's security patches as soon as possible to all affected devices
- If MGCP inspection is not required for your environment, disable the feature as a temporary workaround
- Implement access control lists to restrict MGCP traffic to only trusted sources
Patch Information
Cisco has released software updates that address this vulnerability. Administrators should consult the Cisco Security Advisory for specific fixed software versions and upgrade guidance. The advisory provides detailed information about affected version ranges and the corresponding fixed releases for both ASA Software and Firepower Threat Defense Software.
Workarounds
- Disable MGCP inspection if it is not required in your environment using no inspect mgcp in the policy configuration
- Implement access control policies to restrict MGCP traffic to known, trusted endpoints only
- Consider network segmentation to limit exposure of devices performing MGCP inspection
- Deploy additional network-based intrusion prevention systems to filter malicious MGCP traffic
# Disable MGCP inspection as a workaround (if MGCP is not required)
# Enter configuration mode
configure terminal
# Identify the policy-map applied to your traffic
show service-policy
# Modify the inspection policy to remove MGCP
policy-map global_policy
class inspection_default
no inspect mgcp
# Save the configuration
write memory
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
