CVE-2020-25367 in DIR-823G
Summary
by MITRE • 11/04/2021
A command injection vulnerability was discovered in the HNAP1 protocol in D-Link DIR-823G devices with firmware V1.0.2B05. An attacker is able to execute arbitrary web scripts via shell metacharacters in the Captcha field to Login.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/09/2021
The vulnerability identified as CVE-2020-25367 represents a critical command injection flaw within the HNAP1 protocol implementation of D-Link DIR-823G wireless routers. This issue stems from inadequate input validation and sanitization mechanisms that fail to properly handle malicious payloads submitted through the Captcha field during the login authentication process. The vulnerability exists specifically in firmware version V1.0.2B05, indicating a targeted flaw that affects only this particular revision of the device's software implementation. The HNAP1 protocol serves as a web-based management interface for device configuration, making it a prime target for attackers seeking persistent access to network infrastructure.
The technical exploitation of this vulnerability occurs through the deliberate injection of shell metacharacters into the Captcha field, which then gets processed without proper sanitization by the device's authentication system. This flaw allows an attacker to execute arbitrary commands on the underlying operating system, effectively bypassing the standard authentication mechanisms. The vulnerability manifests as a classic command injection attack vector where user-controllable input is directly incorporated into system commands without proper escaping or filtering. The specific nature of this vulnerability aligns with CWE-77, which categorizes command injection flaws as a direct result of insufficient input validation in application code. The attack surface is particularly concerning as it operates at the web interface level, requiring no physical access to the device and potentially enabling remote exploitation from any location with network connectivity.
The operational impact of this vulnerability extends beyond simple unauthorized access to encompass complete system compromise and potential network infiltration. Once exploited, an attacker gains the ability to execute arbitrary code with the privileges of the web server process, which typically runs with elevated permissions on network devices. This could enable attackers to modify device configuration settings, install malicious firmware, establish persistent backdoors, or use the compromised device as a pivot point for attacking other systems within the local network. The vulnerability creates a persistent threat vector that can be exploited repeatedly, as the authentication bypass allows attackers to maintain access even after initial exploitation. From an attacker's perspective, this vulnerability maps directly to the ATT&CK technique T1059.001 for command and scripting interpreter, specifically through the use of web shell execution and command line interface manipulation.
Mitigation strategies for this vulnerability require immediate firmware updates from D-Link to address the root cause through proper input sanitization and validation. Network administrators should implement network segmentation and access controls to limit exposure of these devices to untrusted networks, while also monitoring for suspicious login attempts and unusual network traffic patterns. The implementation of web application firewalls and intrusion detection systems can help detect and block malicious payloads targeting this specific vulnerability. Additionally, organizations should consider disabling unnecessary web management interfaces and implementing strong authentication mechanisms including multi-factor authentication to reduce the attack surface. Regular vulnerability assessments and penetration testing should be conducted to identify similar flaws in other network infrastructure devices, as this vulnerability demonstrates the importance of proper input validation in embedded systems and web interfaces. The vulnerability also highlights the need for continuous security monitoring and prompt patch management processes to prevent exploitation of known flaws in network infrastructure equipment.