CVE-2018-19989 in DIR-822
Summary
by MITRE
In the /HNAP1/SetQoSSettings message, the uplink parameter is vulnerable, and the vulnerability affects D-Link DIR-822 Rev.B 202KRb06 and DIR-822 Rev.C 3.10B06 devices. In the SetQoSSettings.php source code, the uplink parameter is saved in the /bwc/entry:1/bandwidth and /bwc/entry:2/bandwidth internal configuration memory without any regex checking. And in the bwc_tc_spq_start, bwc_tc_wfq_start, and bwc_tc_adb_start functions of the bwcsvcs.php source code, the data in /bwc/entry:1/bandwidth and /bwc/entry:2/bandwidth is used with the tc command without any regex checking. A vulnerable /HNAP1/SetQoSSettings XML message could have shell metacharacters in the uplink element such as the `telnetd` string.
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Analysis
by VulDB Data Team • 09/17/2023
The vulnerability described in CVE-2018-19989 represents a critical command injection flaw within D-Link DIR-822 wireless routers running specific firmware versions. This vulnerability exists in the HNAP1/SetQoSSettings message processing functionality where the uplink parameter is handled without proper input validation or sanitization. The affected devices DIR-822 Rev.B 202KRb06 and DIR-822 Rev.C 3.10B06 are particularly susceptible due to the absence of regex validation when processing the uplink parameter. The flaw is rooted in the SetQoSSettings.php source code where the uplink parameter is directly written to internal configuration memory locations /bwc/entry:1/bandwidth and /bwc/entry:2/bandwidth without any sanitization measures. This insecure data handling extends to the bwcsvcs.php source code where functions bwc_tc_spq_start, bwc_tc_wfq_start, and bwc_tc_adb_start utilize the data stored in these configuration locations with the tc command, creating a direct path for command injection attacks. The vulnerability is categorized under CWE-78 as a failure to sanitize shell metacharacters, which aligns with the ATT&CK technique T1059.004 for executing malicious commands through shell injection.
The operational impact of this vulnerability is severe as it allows remote attackers to execute arbitrary commands on affected devices with the privileges of the web server process. When a malicious XML message containing shell metacharacters such as the telnetd string is sent to the vulnerable device, the tc command processes these unvalidated inputs, potentially enabling attackers to establish remote access to the router. This command injection vulnerability can be exploited to gain unauthorized access to the device's operating system, allowing for complete compromise of the router's functionality. The attack surface is particularly concerning because HNAP1 (Home Network Administration Protocol) is designed for remote management, making this vulnerability exploitable over the network without requiring physical access to the device.
Mitigation strategies for CVE-2018-19989 should focus on immediate firmware updates from D-Link to address the input validation deficiencies in the affected router models. Network administrators should implement strict network segmentation and access controls to limit exposure of these devices to untrusted networks. Additionally, monitoring for unusual network traffic patterns and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability demonstrates the importance of input validation and proper sanitization of user-supplied data before processing, particularly when dealing with system commands that interface directly with the operating system. Organizations should also consider implementing network-based firewalls to restrict access to the HNAP1 interface and other management protocols, reducing the attack surface for such vulnerabilities. The flaw highlights the need for security-by-design principles in embedded systems where administrative interfaces directly interact with system commands without proper validation mechanisms.