CVE-2026-6560: H3C Magic B0 Router Buffer Overflow

Danger

Executive Summary: CVE-2026-6560 represents a critical vulnerability affecting H3C Magic B0 routers running firmware versions up to 100R002. Due to the lack of proper bounds checking in the web management interface, a remote, unauthenticated attacker can trigger a stack-based buffer overflow. This vulnerability can be exploited to achieve full Remote Code Execution (RCE) on the device or cause a sustained Denial of Service (DoS). Exposed management interfaces are at immediate risk of exploitation by IoT botnets.

1. Technical Vulnerability Analysis

Embedded devices and routers frequently suffer from memory corruption vulnerabilities within their custom HTTP daemons. CVE-2026-6560 is a classic CWE-121: Stack-based Buffer Overflow.

The vulnerability is located in the router’s web management panel, specifically within the endpoint handling SSID configuration changes: /goform/aspForm.

When the backend C/C++ binary processes incoming POST requests, it routes the CMD=Edit_BasicSSID instruction to a specific handler function. This function extracts the value of the param argument and copies it into a fixed-size internal memory buffer (allocated on the stack). Because the developer used an unsafe memory copy function (such as strcpy or sprintf) without validating the length of the user-supplied string, supplying a payload larger than the allocated buffer overwrites adjacent memory spaces, including the saved Instruction Pointer (Instruction Pointer / Return Address).

By carefully crafting the length and content of the param string, an attacker can hijack the execution flow and point it to their own shellcode (RCE), or simply crash the HTTP daemon (DoS).

2. Exploitation Flow

The exploitation requires no authentication, making it highly “wormable” for IoT malware (like Mirai variants).

1. Reconnaissance: The attacker scans the internet (via Shodan or masscan) for exposed H3C Magic B0 web management interfaces (typically running on port 80 or 8080).
2. Payload Crafting: The attacker generates a payload consisting of a massive string of characters (buffer padding) followed by the specific memory address of a ROP (Return-Oriented Programming) gadget, concluding with the shellcode.
3. Delivery: The attacker sends an HTTP POST request to /goform/aspForm containing the malicious param value.
4. Execution: The router’s HTTP daemon processes the request, overflows the stack, and executes the payload with the privileges of the web server (often root on embedded devices).

3. Forensic Investigation & Telemetry

Investigating compromised IoT routers is notoriously difficult because analysts typically do not have SSH access or EDR agents installed on the device. Forensics must pivot to Network Detection and Response (NDR).

• Device Instability: Failed buffer overflow attempts will crash the web service. Monitor network management tools for H3C routers dropping offline, refusing HTTP connections, or unexpectedly rebooting.
• Network Telemetry: Analyze WAF (Web Application Firewall) or Reverse Proxy logs if the router is placed behind one. Look for POST requests directed at /goform/aspForm containing exceptionally large payloads.

4. Detection & Threat Hunting

To protect the network perimeter, deploy the following detection rules on your Intrusion Detection Systems (IDS/IPS) and SIEM.

Suricata / Snort Rule

snort_cve_2026_6560.rules

# Detects the specific URI and the unusually large 'param' payload typical of this buffer overflow
alert tcp $EXTERNAL_NET any -> $HOME_NET $HTTP_PORTS (msg:"EXPLOIT H3C Magic B0 Buffer Overflow Attempt (CVE-2026-6560)"; flow:established,to_server; content:"POST"; http_method; content:"/goform/aspForm"; http_uri; content:"CMD=Edit_BasicSSID"; http_client_body; pcre:"/param=[^&]{256,}/P"; classtype:attempted-admin; sid:1000001; rev:1;)

Sigma (WAF Logs)

sigma_h3c_magic_b0_bof.yaml

title: Potential H3C Magic B0 Buffer Overflow (CVE-2026-6560)
id: 4f8c9b2a-1d3e-5f7g-8h9i-0j1k2l3m4n5o
status: experimental
description: Detects attempts to trigger a buffer overflow in H3C Magic B0 routers via the Edit_BasicSSID parameter in web server or WAF logs.
logsource:
  category: webserver
detection:
  selection:
    http-method: 'POST'
    c-uri|endswith: '/goform/aspForm'
    cs-uri-query|contains: 'CMD=Edit_BasicSSID'
    cs-uri-query|re: 'param=[a-zA-Z0-9%]{256,}'
  condition: selection
level: high
tags:
  - attack.initial_access
  - attack.t1190
  - cve.2026-6560

5. Mitigation and Remediation

1. Firmware Update: Apply the latest firmware patch provided by the vendor immediately.
2. Network Segregation: Never expose router management interfaces to the public internet. Ensure that access to the web administration panel (port 80/443) is strictly limited to dedicated, internal Management VLANs.
3. Disable Remote Management: If remote management over the WAN is enabled on the device, disable it immediately in the device settings.

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Sources & References

• The Hacker Wire: H3C Magic B0 Buffer Overflow (CVE-2026-6560)
• RedPacket Security: CVE Alert CVE-2026-6560 H3C Magic B0
• GitHub Vulnerability Reports: xiaohaiyang-ai / CVE-Reports