D-Link DIR-823X Router Remote Command Injection Vulnerability (CVE-2025-29635) Security Advisory

1. Apply Official Firmware Update

• Visit the official D-Link Support Portal, download the latest secure firmware version for the DIR-823X model, and perform the upgrade.

2. Temporary Mitigations

If immediate patching is not feasible, implement the following workarounds to reduce exposure:

• Disable Remote Management: Ensure that remote WAN-side access to the router's web administration interface (HTTP/HTTPS) is completely disabled.
• Enforce Strong Credentials: Change the default administrator password to a highly complex, unique password to prevent unauthorized access.
• Network Segmentation: Restrict access to the management interface to trusted internal IP addresses only.

3. Indicators of Compromise (IoC) Monitoring

Monitor web server logs for suspicious request patterns targeting the vulnerable endpoint:

POST /goform/set_prohibiting HTTP/1.1
Host: [Router_IP]
Authorization: Basic [Admin_Credentials]
Content-Type: application/x-www-form-urlencoded

# Inspect payload for shell metacharacters like ;, `, or $() used for command injection

This vulnerability (CVE-2025-29635) is a Command Injection vulnerability (CWE-77) residing in the /goform/set_prohibiting endpoint of the D-Link DIR-823X wireless router's web management interface.

An authenticated attacker with administrative privileges can trigger remote command execution by sending a specially crafted HTTP POST request to the vulnerable endpoint. Due to insufficient input validation and sanitization of user-supplied parameters, shell metacharacters (such as ;, |, or backticks) are passed directly to the underlying operating system shell, allowing arbitrary command execution.

This vulnerability is actively exploited in the wild by Mirai botnet campaigns and has been added to the CISA Known Exploited Vulnerabilities (KEV) catalog, carrying a critical EPSS score of 0.94.