H3C Magic B1 Router Buffer Overflow Vulnerability

hello@craftedsignal.io — Sun, 19 Apr 2026 23:16:33 +0000

A critical buffer overflow vulnerability, identified as CVE-2026-6581, affects H3C Magic B1 routers up to version 100R004. The vulnerability resides in the SetMobileAPInfoById function within the /goform/aspForm file. An attacker can exploit this flaw by crafting a malicious request that manipulates the param argument, leading to a buffer overflow and potential remote code execution. This vulnerability is particularly concerning because a public exploit is available, increasing the risk of widespread exploitation. The vendor was notified about the vulnerability but has not responded. Given the ease of exploitation and the potential for complete system compromise, organizations using affected H3C routers should take immediate action.

Attack Chain

The attacker identifies a vulnerable H3C Magic B1 router running a firmware version up to 100R004.
The attacker crafts a malicious HTTP POST request targeting the /goform/aspForm endpoint.
The request includes the SetMobileAPInfoById function call with an overly long value for the param argument, triggering the buffer overflow.
The overflow overwrites adjacent memory regions, including the return address on the stack.
The attacker sets the overwritten return address to point to attacker-controlled code or a ROP chain.
When the SetMobileAPInfoById function returns, execution jumps to the attacker-controlled code.
The attacker’s code executes with elevated privileges, potentially allowing full control of the router.
The attacker can then use the compromised router to establish a foothold within the network, exfiltrate data, or launch further attacks.

Impact

Successful exploitation of CVE-2026-6581 allows a remote attacker to execute arbitrary code with root privileges on the H3C Magic B1 router. This can lead to complete compromise of the device, allowing the attacker to control network traffic, exfiltrate sensitive data, or use the router as a jumping-off point for further attacks within the network. Given the widespread use of these routers in small to medium-sized businesses and homes, a large number of devices are potentially vulnerable. There is no indication of victim counts or sectors targeted at this time.

Recommendation

Deploy the Sigma rule Detect H3C Magic B1 Buffer Overflow Attempt to your SIEM to detect exploitation attempts targeting CVE-2026-6581 via suspicious HTTP POST requests to /goform/aspForm (see Sigma rule below).
Apply appropriate input validation and sanitization measures if you manage the web server to mitigate buffer overflows.
Monitor network traffic for unusual activity originating from H3C Magic B1 routers.
Consider replacing H3C Magic B1 routers with more secure alternatives if updates are not available.

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

hello@craftedsignal.io — Sun, 19 Apr 2026 07:16:05 +0000

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

The attacker identifies a vulnerable H3C Magic B0 router running firmware version 100R002 or earlier.
The attacker crafts a malicious HTTP POST request targeting the /goform/aspForm endpoint.
The POST request includes the Edit_BasicSSID function call.
The param argument within the POST data contains a specially crafted string exceeding the buffer size allocated in the Edit_BasicSSID function.
The buffer overflow occurs when the Edit_BasicSSID function processes the oversized param argument without proper bounds checking.
The overflow overwrites adjacent memory regions, potentially including the return address on the stack.
The attacker gains control of the program execution flow.
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.

H3c — CraftedSignal Threat Feed

H3C Magic B1 Router Buffer Overflow Vulnerability

Attack Chain

Impact

Recommendation

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

Attack Chain

Impact

Recommendation