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

CVE-2026-6560 Overview

A buffer overflow vulnerability has been identified in H3C Magic B0 routers running firmware versions up to 100R002. This vulnerability affects the Edit_BasicSSID function within the /goform/aspForm file. Attackers can exploit this flaw by manipulating the param argument, leading to a buffer overflow condition that can be triggered remotely over the network.

The exploit has been publicly disclosed, and the vendor was contacted early about this disclosure but did not respond. This lack of vendor response increases the risk profile for organizations using affected devices.

Critical Impact

Remote attackers with low privileges can exploit this buffer overflow to potentially achieve arbitrary code execution on affected H3C Magic B0 routers, compromising network infrastructure security.

Affected Products

• H3C Magic B0 (firmware versions up to 100R002)

Discovery Timeline

• 2026-04-19 - CVE-2026-6560 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6560

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in the web management interface of H3C Magic B0 routers, specifically within the Edit_BasicSSID function that processes SSID configuration requests.

When a malicious request is sent to the /goform/aspForm endpoint, the param argument is not properly validated for length or content. This allows an attacker to supply an oversized or specially crafted input that exceeds the allocated buffer space, resulting in memory corruption.

The network-accessible attack vector combined with low complexity requirements makes this vulnerability particularly concerning for organizations with exposed router management interfaces.

Root Cause

The root cause of this vulnerability is improper boundary checking in the Edit_BasicSSID function. The function fails to validate the length of the param argument before copying it into a fixed-size buffer. This classic buffer overflow condition occurs because:

1. User-supplied input from the web form is accepted without length validation
2. The input is copied to a stack or heap buffer with insufficient size checking
3. Oversized input overwrites adjacent memory regions

This improper restriction of operations within memory bounds (CWE-119) can lead to memory corruption, denial of service, or potentially arbitrary code execution.

Attack Vector

The attack can be executed remotely over the network by sending a crafted HTTP request to the router's web management interface. An authenticated attacker with low privileges can exploit this vulnerability by:

1. Accessing the web management interface at /goform/aspForm
2. Submitting a malicious request targeting the Edit_BasicSSID function
3. Including an oversized or specially crafted param argument
4. Triggering the buffer overflow condition

The vulnerability requires network access and low-level authentication, but does not require user interaction. For detailed technical analysis, refer to the GitHub Vulnerability Report and VulDB Entry #358197.

Detection Methods for CVE-2026-6560

Indicators of Compromise

• Unusual HTTP POST requests to /goform/aspForm with abnormally large param values
• Unexpected router reboots or crashes that may indicate exploitation attempts
• Anomalous network traffic patterns targeting the router management interface
• Evidence of unauthorized configuration changes to SSID settings

Detection Strategies

• Monitor web server logs for oversized requests to the /goform/aspForm endpoint
• Implement intrusion detection rules to flag requests with unusually long parameter values targeting Edit_BasicSSID
• Deploy network-based anomaly detection for traffic patterns consistent with buffer overflow exploitation
• Review authentication logs for unusual access patterns to the router management interface

Monitoring Recommendations

• Enable verbose logging on H3C Magic B0 devices if available
• Configure network monitoring tools to alert on suspicious traffic to router management ports
• Implement SIEM rules to correlate multiple failed or anomalous requests to /goform/aspForm
• Regularly audit device configurations for unauthorized changes

How to Mitigate CVE-2026-6560

Immediate Actions Required

• Restrict network access to the router management interface using firewall rules or ACLs
• Disable remote management access if not operationally required
• Implement network segmentation to isolate management interfaces from untrusted networks
• Monitor for exploitation attempts using the detection strategies outlined above

Patch Information

At the time of this publication, H3C has not responded to disclosure attempts and no official patch has been released. Organizations should prioritize implementing workarounds and network-level protections until a vendor patch becomes available.

Monitor the VulDB Entry and official H3C security advisories for updates on patch availability.

Workarounds

• Disable remote web management access and use local console access only
• Implement strict IP-based access control lists (ACLs) limiting management interface access to trusted administrator workstations
• Deploy a web application firewall (WAF) in front of the management interface to filter malicious requests
• Consider replacing affected devices with alternative products from vendors with better security response practices

# Example: Restrict management interface access via firewall (adjust for your environment)
# Block external access to router management port (typically 80/443)
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP