CVE-2026-12495 Mercusys CVE debrief

Who should care

Administrators and users of the Mercusys MB115-4G device should be aware of this critical vulnerability. An unauthenticated attacker could exploit this vulnerability to cause a denial of service.

Technical summary

The CVE-2026-12495 vulnerability is caused by a stack buffer overflow in the http_gdpr_decrypt function of the Mercusys MB115-4G device's web interface. An unauthenticated attacker could exploit this vulnerability by sending a specially crafted request to the /cgi/login endpoint, causing memory corruption and the httpd process to crash, resulting in a denial of service for the web administration service. The CVSS score for this vulnerability is 9.2, indicating a critical severity.

Defensive priority

High priority should be given to addressing this vulnerability, as it is critical and could allow an unauthenticated attacker to cause a denial of service. Immediate action is required to protect against potential exploitation attempts, especially in environments where the Mercusys MB115-4G device is exposed to the internet or untrusted networks. Implementing compensating controls and closely monitoring for suspicious activity can help mitigate the risk until a patch is applied. Additionally, administrators should review system logs for signs of exploitation and ensure that all security patches are up to date. Given the critical nature of this vulnerability, it is essential to prioritize its remediation and allocate necessary resources promptly. This may involve coordinating with vendors for patch availability, testing patches before deployment, and ensuring that affected systems are properly configured and secured. The vulnerability's impact on business operations could be significant if exploited, making swift and effective response crucial. Therefore, assigning ownership for follow-up and tracking the remediation progress is vital to ensure that the vulnerability is addressed in a timely manner. By taking these steps, organizations can reduce the risk associated with CVE-2026-12495 and protect their systems from potential attacks. It is also important to note that while the CVE record provides valuable information, it may not cover all aspects of the vulnerability or its potential impact. Therefore, defenders should remain vigilant and continuously assess their exposure to this and similar vulnerabilities. To further enhance security, consider implementing additional security measures such as network segmentation, intrusion detection systems, and regular security audits. By adopting a proactive and layered approach to security, organizations can better protect themselves against the exploitation of CVE-2026-12495 and other vulnerabilities. Furthermore, staying informed about the latest developments and updates related to this vulnerability is crucial to ensure that the most effective mitigation strategies are employed. This includes monitoring vendor advisori

Recommended defensive actions

• Inventory and verify affected scope of Mercusys MB115-4G devices
• Apply vendor remediation or patches if available
• Implement compensating controls such as monitoring and exception tracking
• Restrict access to the web administration service
• Monitor for suspicious requests to the /cgi/login endpoint

Evidence notes

The CVE record was published on 2026-07-27T12:16:41.027Z and has not been modified since then. The NVD entry is currently available. The vulnerability details are based on the provided source corpus, which includes information from Incibe and the NVD. Evidence is limited to public sources and may not reflect the full scope or impact of the vulnerability. Defenders should verify affected systems and apply patches or mitigations as recommended by the vendor.

Official resources