CVE-2025-10392: Mercury WiFi Router Buffer Overflow Flaw

CVE-2025-10392 Overview

A stack-based buffer overflow vulnerability has been identified in the Mercury KM08-708H GiGA WiFi Wave2 router running firmware version 1.1.14. This vulnerability exists within the HTTP Header Handler component, specifically in the processing of the Host header argument. An unauthenticated remote attacker can exploit this flaw to cause a buffer overflow condition, potentially leading to arbitrary code execution or device compromise.

Critical Impact

Remote attackers can exploit this vulnerability without authentication to potentially execute arbitrary code on vulnerable IoT devices, compromising network infrastructure integrity.

Affected Products

• Mercury KM08-708H GiGA WiFi Wave2 firmware version 1.1.14
• KT GIGA WiFi-Wave 2 router devices

Discovery Timeline

• September 14, 2025 - CVE-2025-10392 published to NVD
• September 15, 2025 - Last updated in NVD database

Technical Details for CVE-2025-10392

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The affected HTTP Header Handler component fails to properly validate the length of input provided in the Host header before copying it to a fixed-size stack buffer. When an attacker supplies an excessively long Host header value, the data overflows the allocated buffer, corrupting adjacent stack memory including saved return addresses and other critical data structures.

The network-accessible nature of this vulnerability means attackers can remotely target vulnerable devices without requiring any prior authentication or user interaction. A public exploit is available, increasing the risk of active exploitation in the wild.

Root Cause

The root cause stems from improper bounds checking in the HTTP Header Handler when processing the Host header argument. The vulnerable code copies user-controlled input from HTTP requests directly into a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern allows attackers to overwrite stack memory with attacker-controlled data.

Attack Vector

The attack is network-based and can be executed remotely against the device's HTTP management interface. An attacker crafts a malicious HTTP request containing an oversized Host header, sending it to the vulnerable router. The HTTP Header Handler processes this malicious input, triggering the stack buffer overflow.

The exploitation mechanism involves sending HTTP requests with manipulated Host header values that exceed the expected buffer size. When the vulnerable parsing function processes this oversized input, it overflows the stack buffer, potentially allowing the attacker to hijack control flow and execute arbitrary code with the privileges of the web service process. Technical details are available in the GitHub Vulnerability Report.

Detection Methods for CVE-2025-10392

Indicators of Compromise

• Unusual HTTP requests with abnormally long Host header values targeting router management interfaces
• Unexpected device crashes, reboots, or service interruptions on Mercury KM08-708H routers
• Anomalous outbound connections from router devices to unknown external IP addresses
• Suspicious process execution or configuration changes on affected devices

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests with excessively long Host headers (exceeding 256+ bytes)
• Monitor for repeated connection attempts to router management interfaces from unusual source IPs
• Deploy packet inspection to detect malformed HTTP headers targeting embedded device web services
• Utilize behavioral analysis to identify routers exhibiting abnormal network traffic patterns

Monitoring Recommendations

• Enable logging on router management interfaces and review for suspicious access patterns
• Implement network segmentation to isolate IoT devices from critical network infrastructure
• Deploy network monitoring solutions capable of inspecting traffic to embedded device management interfaces
• Establish baseline network behavior for router devices to detect anomalous activity

How to Mitigate CVE-2025-10392

Immediate Actions Required

• Restrict access to the router's HTTP management interface to trusted internal networks only
• Implement firewall rules to block external access to the device's management ports
• Consider disabling remote management features if not required
• Monitor for firmware updates from Mercury/KT addressing this vulnerability

Patch Information

At the time of publication, no official vendor patch has been confirmed. Organizations should monitor official Mercury and KT channels for security updates addressing this stack-based buffer overflow vulnerability in firmware version 1.1.14. Additional vulnerability tracking information is available through VulDB #323827.

Workarounds

• Disable HTTP-based remote management and use local-only management interfaces where possible
• Place vulnerable devices behind a firewall with strict ingress filtering to block external access to management services
• Implement network access control lists (ACLs) to restrict management interface access to authorized administrator IP addresses only
• Consider replacing affected devices with alternatives that receive active security support if no patch becomes available

# Network-level mitigation: Block external access to router management
# Add firewall rule to restrict HTTP management access (example iptables)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP