CVE-2020-8809 in GXDLMS Director
Summary
by MITRE
Gurux GXDLMS Director prior to 8.5.1905.1301 downloads updates to add-ins and OBIS code over an unencrypted HTTP connection. A man-in-the-middle attacker can prompt the user to download updates by modifying the contents of gurux.fi/obis/files.xml and gurux.fi/updates/updates.xml. Then, the attacker can modify the contents of downloaded files. In the case of add-ins (if the user is using those), this will lead to code execution. In case of OBIS codes (which the user is always using as they are needed to communicate with the energy meters), this can lead to code execution when combined with CVE-2020-8810.
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Analysis
by VulDB Data Team • 04/06/2024
The vulnerability identified as CVE-2020-8809 affects Gurux GXDLMS Director versions prior to 8.5.1905.1301, presenting a critical security flaw in the software's update mechanism. This issue stems from the application's reliance on unencrypted HTTP connections for downloading add-ins and OBIS code updates from the gurux.fi domain. The fundamental technical flaw lies in the absence of transport layer security, making the communication channel susceptible to interception and modification by malicious actors positioned between the user and the update servers. The vulnerability operates through a man-in-the-middle attack vector where an attacker can manipulate the update process by modifying the XML files that contain update metadata, specifically gurux.fi/obis/files.xml and gurux.fi/updates/updates.xml. This manipulation allows the attacker to redirect users to maliciously modified update files that can be seamlessly integrated into the application's operation without user suspicion.
The operational impact of this vulnerability extends beyond simple data interception, creating a pathway for arbitrary code execution within the context of the targeted system. When users download and install modified add-ins, the malicious code embedded within these components can execute with the privileges of the application, potentially leading to complete system compromise. The severity is amplified by the fact that OBIS codes are essential for communication with energy meters, making them an integral part of the application's core functionality. The vulnerability becomes particularly dangerous when combined with CVE-2020-8810, which represents a separate but complementary weakness that allows for code execution when OBIS codes are processed. This combination creates a multi-stage attack vector where an attacker first uses CVE-2020-8809 to deliver malicious components and then leverages CVE-2020-8810 to execute code within the application context. The attack requires minimal user interaction beyond normal update acceptance, making it particularly insidious as it can exploit the trust relationship between the application and its update servers.
The security implications of this vulnerability align with CWE-319, which addresses the exposure of sensitive information through improper use of network connections, and represents a clear violation of secure communication practices. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for command and scripting interpreter usage and T1021.002 for remote services, as the attack exploits legitimate update mechanisms to gain remote code execution capabilities. Organizations using Gurux GXDLMS Director should prioritize immediate mitigation by upgrading to version 8.5.1905.1301 or later, which implements encrypted HTTPS connections for all update downloads. Additional protective measures include implementing network monitoring to detect unauthorized modifications to update servers, configuring firewall rules to restrict access to the vulnerable update endpoints, and establishing manual verification procedures for all downloaded components. The vulnerability demonstrates the critical importance of secure update mechanisms in industrial control systems and highlights the need for end-to-end encryption of all communication channels that handle software distribution and system configuration data.