CVE-2019-3971 in Comodo
Summary
by MITRE
Comodo Antivirus versions up to 12.0.0.6810 are vulnerable to a local Denial of Service affecting CmdVirth.exe via its LPC port "cmdvrtLPCServerPort". A low privileged local process can connect to this port and send an LPC_DATAGRAM, which triggers an Access Violation due to hardcoded NULLs used for Source parameter in a memcpy operation that is called for this handler. This results in CmdVirth.exe and its child svchost.exe instances to terminate.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/01/2023
The vulnerability identified as CVE-2019-3971 represents a critical local denial of service flaw within Comodo Antivirus software version 12.0.0.6810 and earlier. This vulnerability specifically targets the CmdVirth.exe component which operates as a core service within the antivirus suite. The affected system employs a Named Pipe communication mechanism through the LPC (Local Procedure Call) port named "cmdvrtLPCServerPort" to facilitate inter-process communication. The flaw exists in how the system handles incoming LPC_DATAGRAM messages, creating a pathway for malicious local processes to exploit the software's memory management functions.
The technical root cause of this vulnerability lies in improper memory handling within the CmdVirth.exe process. When a local process connects to the designated LPC port and sends an LPC_DATAGRAM, the system's handler function processes this communication without adequate validation of the source parameters. The vulnerability stems from the use of hardcoded NULL values in the Source parameter of a memcpy operation, which is a well-known pattern that leads to memory corruption. This specific implementation flaw creates an access violation condition when the memcpy function attempts to copy data from a NULL pointer, resulting in a segmentation fault that terminates the targeted process.
The operational impact of this vulnerability extends beyond simple service disruption as it affects the stability of the entire antivirus infrastructure. When CmdVirth.exe terminates due to the access violation, it cascades to affect svchost.exe instances that are children of this process, causing a broader system instability. This vulnerability is particularly concerning because it requires only low privilege local access to exploit, making it accessible to any user account on the system. The flaw essentially allows an attacker to cause a denial of service condition that can persistently disrupt antivirus functionality, potentially leaving the system vulnerable to other threats during the service interruption period.
This vulnerability maps directly to CWE-121, which addresses stack-based buffer overflow conditions, and more specifically to CWE-125, which covers out-of-bounds read conditions. The flaw also aligns with ATT&CK technique T1489, which describes creating or manipulating system services to disrupt availability. From a security perspective, the vulnerability demonstrates poor input validation and memory management practices that are commonly exploited in privilege escalation and denial of service scenarios. The exploitation process is straightforward and requires minimal resources, making it particularly dangerous in environments where antivirus services are critical for system protection.
The recommended mitigation strategies include immediate deployment of the vendor-provided patch or update that addresses the memory handling issue in CmdVirth.exe. System administrators should also implement monitoring for unauthorized connections to the LPC port and consider restricting local process access to critical system services. Additional protective measures include implementing process isolation techniques, using application whitelisting to prevent unauthorized execution, and maintaining regular system updates to address similar vulnerabilities. Organizations should also conduct security assessments to identify other potential LPC port vulnerabilities and ensure that all antivirus and security software components are regularly updated to prevent exploitation of similar memory corruption flaws.