H3C Magic B0 Buffer Overflow Vulnerability (CVE-2026-9393)

A buffer overflow vulnerability, identified as CVE-2026-9393, has been discovered in H3C Magic B0 devices up to version 100R002. The vulnerability resides within the Edit_BasicSSID_5G function of the /goform/aspForm file. Successful exploitation allows remote attackers to potentially execute arbitrary code on the affected device. The vulnerability was reported to the vendor, but there has been no response. Public exploits are available, increasing the risk of exploitation. This poses a significant security risk to organizations using affected H3C devices, especially since the attack can be initiated remotely without authentication in some configurations.

Attack Chain

1. The attacker identifies an H3C Magic B0 device with firmware version up to 100R002 exposed to the network.
2. The attacker crafts a malicious HTTP request targeting the /goform/aspForm endpoint.
3. The crafted request includes the Edit_BasicSSID_5G function call with an overly long string in the param argument.
4. The device’s web server processes the request without proper bounds checking on the param argument.
5. The overly long param value overflows the buffer allocated for it in memory.
6. The buffer overflow overwrites adjacent memory regions, potentially including critical program data or code execution pointers.
7. The attacker gains arbitrary code execution on the device.
8. The attacker can then leverage the compromised device for further malicious activities, such as data exfiltration or lateral movement within the network.

Impact

Successful exploitation of CVE-2026-9393 can lead to complete compromise of the H3C Magic B0 device. Given that these devices often act as network gateways or access points, a compromised device can be used to eavesdrop on network traffic, launch attacks against other devices on the network, or create a persistent backdoor. While the exact number of vulnerable devices is unknown, the public availability of exploits makes this a high-risk vulnerability that requires immediate attention.

Recommendation

• Apply any available patches or firmware updates released by H3C to address CVE-2026-9393.
• If patches are unavailable, consider implementing network segmentation to limit the exposure of H3C Magic B0 devices.
• Monitor network traffic for suspicious HTTP requests targeting the /goform/aspForm endpoint with unusually long param arguments. Deploy the Sigma rule Detect H3C Magic B0 CVE-2026-9393 Attempt to detect potential exploitation attempts.
• Implement access control lists to restrict access to H3C Magic B0 devices to only authorized personnel or systems.
• Enable logging on H3C Magic B0 devices, where available, and forward logs to a SIEM for analysis.