CVE-2026-10259: H3C Magic B0 Buffer Overflow Vulnerability

CVE-2026-10259 Overview

CVE-2026-10259 is a stack-based buffer overflow vulnerability affecting H3C Magic B0 routers up to firmware version 100R002. The flaw resides in the SetMobileAPInfoById function within the /goform/aspForm endpoint. Manipulation of the param argument triggers the overflow condition, allowing remote attackers to corrupt stack memory. The vulnerability is categorized under [CWE-119] for improper restriction of operations within memory buffer bounds. A public proof-of-concept exists, and the vendor did not respond to disclosure attempts.

Critical Impact

Remote attackers with low privileges can exploit the stack-based buffer overflow over the network to compromise confidentiality, integrity, and availability of affected H3C Magic B0 devices.

Affected Products

• H3C Magic B0 router firmware up to version 100R002
• Web management interface endpoint /goform/aspForm
• SetMobileAPInfoById function within the device firmware

Discovery Timeline

• 2026-06-01 - CVE-2026-10259 published to NVD
• 2026-06-01 - Last updated in NVD database
• Vendor contact - H3C was contacted prior to disclosure but did not respond

Technical Details for CVE-2026-10259

Vulnerability Analysis

The vulnerability exists in the request handler for the SetMobileAPInfoById function exposed through the /goform/aspForm web interface on H3C Magic B0 routers. The handler accepts a user-supplied param argument and copies its contents into a fixed-size stack buffer without enforcing length validation. When an attacker supplies an oversized param value, the copy operation writes beyond the buffer boundary and overwrites adjacent stack memory, including saved return addresses and frame pointers.

The exploit has been publicly disclosed via a GitHub PoC Repository, increasing the likelihood of opportunistic exploitation against exposed devices. EPSS data places the exploitation probability at 0.082% as of 2026-06-04.

Root Cause

The root cause is the absence of bounds checking on the param request parameter before it is copied into a stack-allocated buffer inside SetMobileAPInfoById. The function relies on unsafe string-handling routines that do not validate the length of attacker-controlled input. This pattern is classified under [CWE-119] as improper restriction of operations within the bounds of a memory buffer.

Attack Vector

Exploitation requires network access to the router's HTTP management interface and authenticated low-privilege access. An attacker sends a crafted HTTP request to /goform/aspForm invoking the SetMobileAPInfoById action with an oversized param value. The overflow corrupts the stack and can be leveraged to redirect execution flow, leading to arbitrary code execution within the embedded firmware context. Routers exposed to the internet through their management interface are at highest risk.

No verified exploitation code is reproduced here. Refer to the VulDB CVE-2026-10259 entry and the linked GitHub Repository Main for technical PoC details.

Detection Methods for CVE-2026-10259

Indicators of Compromise

• HTTP POST requests to /goform/aspForm containing the SetMobileAPInfoById action with abnormally long param values
• Unexpected router reboots, crashes, or web management interface unavailability following HTTP requests
• Outbound connections from the router to unknown external hosts, indicating possible post-exploitation activity
• Unauthorized configuration changes to mobile AP settings on H3C Magic B0 devices

Detection Strategies

• Inspect inbound HTTP traffic to router management interfaces for oversized parameters targeting /goform/aspForm
• Apply intrusion detection signatures that flag overlong param field values in requests to the aspForm endpoint
• Correlate authentication events on the router with subsequent administrative HTTP requests to identify suspicious sequences

Monitoring Recommendations

• Forward router syslog, authentication logs, and HTTP access logs to a centralized SIEM for retention and correlation
• Baseline normal administrative request sizes and alert on statistical outliers in param length
• Monitor for new or unexpected listening ports and outbound connections originating from H3C Magic B0 devices

How to Mitigate CVE-2026-10259

Immediate Actions Required

• Restrict access to the router's web management interface to trusted management networks only and block external exposure
• Disable remote management on the WAN interface of affected H3C Magic B0 routers
• Rotate administrative credentials and enforce strong, unique passwords on management accounts
• Audit router configurations for unauthorized changes to mobile AP and related settings

Patch Information

No vendor patch has been published. According to the disclosure, H3C was notified but did not respond. Organizations operating affected H3C Magic B0 firmware up to 100R002 should monitor the vendor's security advisories for future updates and consider replacement if a fix is not released. Refer to VulDB Vulnerability #367539 for ongoing tracking.

Workarounds

• Place affected routers behind a network firewall that filters inbound HTTP and HTTPS traffic to the management interface
• Apply access control lists permitting administrative access only from designated management IP addresses
• Segment vulnerable devices into an isolated VLAN to limit lateral movement opportunities if compromise occurs
• Consider replacing affected H3C Magic B0 devices with supported hardware that receives active security maintenance

# Example: restrict router management access using upstream firewall rules
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <mgmt_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -s <mgmt_subnet> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -j DROP