Executive Summary

[{'type': 'paragraph', 'content': "CVE-2026-2063 is a remote OS command injection vulnerability in the D-Link DIR-823X router's web management interface, specifically at the /goform/set_ac_server endpoint."}, {'type': 'paragraph', 'content': 'The vulnerability arises because the input parameter ac_server is not properly validated. The blacklist filter used to block dangerous characters does not include newline characters (\\n), which in Linux shells act as command separators.'}, {'type': 'paragraph', 'content': 'An authenticated attacker can inject a newline character to terminate the intended command and start a new arbitrary command, which is executed with root privileges on the device.'}, {'type': 'paragraph', 'content': 'This flaw allows attackers to execute arbitrary system commands remotely on the affected router.'}] [1, 2, 3]

Useful 0 Not Useful 0

Impact Analysis

This vulnerability allows an authenticated remote attacker to execute arbitrary commands with root privileges on the affected D-Link DIR-823X router.

• Compromise of device confidentiality by accessing sensitive information.
• Integrity violations by modifying system configurations or data.
• Availability impact by executing commands that disrupt normal device operation.

Because the attacker gains root-level access, the entire device and potentially the network it manages can be compromised.

Useful 0 Not Useful 0

Compliance Impact

I don't know

Useful 0 Not Useful 0

Detection Guidance

[{'type': 'paragraph', 'content': "This vulnerability can be detected by attempting to exploit the command injection flaw in the /goform/set_ac_server endpoint of the D-Link DIR-823X router's web management interface. A common detection method involves sending a specially crafted request with the ac_server parameter containing a newline character followed by a benign command such as 'sleep 3'. If the response time is delayed accordingly, it indicates successful command injection."}, {'type': 'paragraph', 'content': "A practical approach is to authenticate to the router's web interface and then send a request to /goform/set_ac_server with a payload like: ac_server=valid_input\\nsleep 3. Measuring the response delay can confirm the vulnerability."}, {'type': 'paragraph', 'content': 'No specific ready-made commands are provided, but the proof-of-concept involves using scripts (e.g., Python) to automate authentication and send the payload to test for command injection.'}] [1]

Useful 0 Not Useful 0

Mitigation Strategies

[{'type': 'paragraph', 'content': "Immediate mitigation steps include restricting access to the router's web management interface to trusted users only, ensuring strong authentication to prevent unauthorized access."}, {'type': 'paragraph', 'content': 'It is recommended to avoid using the vulnerable /goform/set_ac_server endpoint or disable the web management interface if possible until a patch is available.'}, {'type': 'paragraph', 'content': 'Longer-term mitigations suggested include expanding the blacklist of forbidden characters in the input validation to include newline (\\n), carriage return (\\r), and other shell metacharacters such as $, &, |, >, and <.'}, {'type': 'paragraph', 'content': 'Replacing vulnerable system calls with secure APIs like parameterized execution functions (e.g., execve()) or using native UCI library APIs to modify configurations without invoking a shell is advised to eliminate the command injection vector.'}, {'type': 'paragraph', 'content': 'If no patch is available, consider replacing the affected product with an alternative device not vulnerable to this issue.'}] [1, 2]

Useful 0 Not Useful 0