H3C Magic B3 Buffer Overflow Vulnerability (CVE-2026-8764)

A buffer overflow vulnerability, identified as CVE-2026-8764, affects H3C Magic B3 devices up to version 100R002. The vulnerability is located within the UpdateWanParams function of the /goform/aspForm file. Successful exploitation of this flaw allows remote attackers to trigger a buffer overflow by manipulating the param argument. Publicly available exploits exist, increasing the risk of active exploitation. The vendor was notified about this vulnerability, but has not responded. This vulnerability allows for unauthenticated remote code execution if successfully exploited.

Attack Chain

1. Attacker identifies an H3C Magic B3 device running a vulnerable firmware version (<= 100R002) accessible over the network.
2. Attacker crafts a malicious HTTP POST request targeting the /goform/aspForm endpoint.
3. The POST request includes the UpdateWanParams function call with a crafted param argument designed to cause a buffer overflow.
4. The device processes the malicious param argument without proper bounds checking.
5. The excessive data in the param argument overwrites adjacent memory regions in the device’s memory space.
6. The attacker carefully crafts the overflowed data to overwrite critical program data, such as return addresses or function pointers.
7. Upon function return, the hijacked execution flow redirects the program to attacker-controlled code.
8. Attacker achieves remote code execution on the device, potentially leading to complete system compromise.

Impact

Successful exploitation of CVE-2026-8764 allows an unauthenticated remote attacker to execute arbitrary code on the affected H3C Magic B3 device. This can lead to a complete compromise of the device, potentially enabling attackers to gain unauthorized access to the network, steal sensitive information, or use the device as a bot in a larger attack. Given the lack of vendor response, a large number of devices may be vulnerable.

Recommendation

• Deploy the Sigma rule Detect CVE-2026-8764 Exploitation Attempt to your SIEM system to detect HTTP requests attempting to exploit the buffer overflow in the UpdateWanParams function of the /goform/aspForm file.
• Monitor web server logs for suspicious POST requests to /goform/aspForm containing unusually long param arguments, as highlighted in the Sigma rule and overview.
• Given the affected product is H3C Magic B3, network administrators should investigate whether any deployed devices are affected.
• Consult the references from NVD to determine if there are any vendor mitigations.