H3C Magic B0 Router Buffer Overflow Vulnerability (CVE-2026-6560)

A critical buffer overflow vulnerability (CVE-2026-6560) has been identified in H3C Magic B0 routers, specifically in versions up to 100R002. The vulnerability resides within the Edit_BasicSSID function of the /goform/aspForm file. An attacker can remotely exploit this flaw by crafting malicious input to the param argument, leading to arbitrary code execution on the device. Public exploits are reportedly available, increasing the risk of widespread exploitation. The vendor was notified about this vulnerability, but has not provided any response or patch as of April 2026. This poses a significant risk to users of the affected H3C Magic B0 routers.

Attack Chain

1. The attacker identifies a vulnerable H3C Magic B0 router running firmware version 100R002 or earlier.
2. The attacker crafts a malicious HTTP POST request targeting the /goform/aspForm endpoint.
3. The POST request includes the Edit_BasicSSID function call.
4. The param argument within the POST data contains a specially crafted string exceeding the buffer size allocated in the Edit_BasicSSID function.
5. The buffer overflow occurs when the Edit_BasicSSID function processes the oversized param argument without proper bounds checking.
6. The overflow overwrites adjacent memory regions, potentially including the return address on the stack.
7. The attacker gains control of the program execution flow.
8. The attacker executes arbitrary code on the router, potentially gaining full control of the device, exfiltrating data, or using it as a pivot point for further attacks.

Impact

Successful exploitation of this buffer overflow vulnerability (CVE-2026-6560) allows a remote attacker to execute arbitrary code on the affected H3C Magic B0 router. This could lead to a complete compromise of the device, including the ability to modify router settings, intercept network traffic, and potentially gain access to connected devices on the network. Given the availability of public exploits, widespread exploitation is possible, potentially impacting a large number of home and small business networks.

Recommendation

• Monitor web server logs for suspicious POST requests to /goform/aspForm with unusually long param arguments (refer to the Attack Chain section).
• Implement rate limiting for requests to /goform/aspForm to mitigate potential exploitation attempts (refer to the Attack Chain section).
• Deploy the following Sigma rule to detect exploitation attempts targeting the vulnerable Edit_BasicSSID function.
• Block network traffic originating from or destined to H3C Magic B0 devices until a patch is available.