CVE-2020-20249 in MikroTik
Summary
by MITRE • 07/20/2021
Mikrotik RouterOs before stable 6.47 suffers from a memory corruption vulnerability in the resolver process. By sending a crafted packet, an authenticated remote attacker can cause a Denial of Service.
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Analysis
by VulDB Data Team • 07/22/2021
The vulnerability identified as CVE-2020-20249 affects MikroTik RouterOS versions prior to stable release 6.47, specifically targeting the resolver process within the network operating system. This memory corruption flaw represents a significant security concern for network infrastructure devices that rely on MikroTik routers for their operations. The vulnerability manifests when the system processes certain network packets through its DNS resolution mechanisms, creating conditions that can lead to system instability and service disruption.
The technical implementation of this vulnerability involves a memory corruption issue within the resolver component that handles DNS queries and responses. When an authenticated remote attacker sends specifically crafted packets to the affected router, the memory management routines within the resolver process fail to properly handle the malformed data structures. This improper handling leads to memory corruption that can cause the resolver process to crash or behave unpredictably. The vulnerability requires authentication to exploit, meaning that an attacker must first establish valid credentials to access the router's management interface before being able to trigger the memory corruption.
The operational impact of CVE-2020-20249 extends beyond simple denial of service, as it can potentially disrupt network connectivity and compromise the reliability of critical infrastructure services. When the resolver process crashes due to memory corruption, it affects DNS resolution capabilities for the entire network segment managed by the compromised router. This can lead to cascading failures where dependent services that rely on DNS resolution become unavailable, potentially affecting multiple systems and applications across the network. The vulnerability's authenticated nature means that unauthorized access to router credentials could enable attackers to cause sustained disruption, making proper credential management and access controls essential for mitigation.
Network administrators should prioritize patching affected MikroTik devices with RouterOS version 6.47 or later, which contains the necessary fixes for this memory corruption vulnerability. The remediation process requires updating the router's firmware to the patched version, which typically involves downloading the appropriate update image from MikroTik's official website and applying it through the router's web interface or command-line interface. Organizations should also implement monitoring solutions to detect unusual network traffic patterns that might indicate exploitation attempts, as well as enforce strict access controls and credential policies to prevent unauthorized access to router management interfaces. Additionally, network segmentation and firewall rules should be configured to limit management access to trusted administrative networks only, reducing the attack surface for potential exploitation of this vulnerability.
This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of memory safety issues in network infrastructure software. From an attacker's perspective, this vulnerability maps to the ATT&CK technique T1071.004 for application layer protocol tunneling, as the exploitation involves crafting network packets to trigger the memory corruption. The vulnerability also relates to T1489, which covers denial of service attacks, as the primary impact is system unavailability through process termination. The authenticated requirement for exploitation means that this vulnerability fits within the broader category of privilege escalation and lateral movement techniques, as attackers must first gain access to valid credentials before being able to cause the denial of service condition. Organizations should consider this vulnerability as part of their overall security posture assessment, particularly in environments where router availability is critical for business operations.