CVE-2025-70023

Executive Summary

CVE-2025-70023 is a critical vulnerability in Transloadit Uppy v0.25.6, stemming from CWE-843 (Access of Resource Using Incompatible Type). This flaw allows an unauthenticated attacker to remotely execute arbitrary code or cause a denial of service by exploiting type confusion during resource access. With a CVSS score of 9.8, the vulnerability poses severe risks to confidentiality, integrity, and availability. No public proof-of-concept or patch is currently available, making it a high-priority zero-day for affected systems.

Supply Chain & Package Security

Uppy is an open-source JavaScript file uploader widely used in web applications. As an NPM package, this vulnerability impacts the software supply chain. Organizations using Uppy v0.25.6 should treat it as a compromised dependency and immediately isolate or upgrade to a patched version once available. Monitor for malicious packages mimicking Uppy in registries.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Exploit does not cross trust boundaries.
• Confidentiality (C): High (H) – Full data disclosure possible.
• Integrity (I): High (H) – Full data modification possible.
• Availability (A): High (H) – Full system denial of service possible.

Threat Level: Critical. Immediate action required.

Deep Dive & Mechanics

CWE-843 (Access of Resource Using Incompatible Type) occurs when a program accesses a resource using an incompatible type, leading to type confusion. In Uppy v0.25.6, this manifests during file upload processing where the application incorrectly interprets user-supplied data as a different type than intended. An attacker can craft a malicious payload that, when processed, triggers memory corruption or logic errors, enabling arbitrary code execution or crashes.

The vulnerability likely resides in the file parsing or validation logic, where type checks are insufficient. For example, a file object might be treated as a string or buffer without proper validation, allowing injection of executable code.

Vulnerable vs. Patched Code

Since no patch is available, the following illustrates the vulnerable pattern and a hypothetical fix.

Vulnerable Code (Uppy v0.25.6):

// Vulnerable: No type checking before using resource
function processFile(file) {
  // file is expected to be an object, but could be a string
  let data = file.data; // Type confusion if file is a string
  // ... process data
}

Patched Code (Hypothetical):

// Patched: Validate type before access
function processFile(file) {
  if (typeof file !== 'object' || file === null) {
    throw new Error('Invalid file type');
  }
  let data = file.data;
  // ... process data
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a vulnerable instance of Uppy v0.25.6 (e.g., using Docker or a Node.js server).
2. Craft a malicious payload that triggers type confusion (e.g., sending a string instead of a file object).
3. Use a tool like Burp Suite or custom Python script to send the payload.

Exploit Script (Python):

import requests

url = "http://target.com/upload"
# Malicious payload: send a string instead of a file object
payload = {"file": "malicious_code"}
response = requests.post(url, data=payload)
print(response.text)

Expected Outcome: The server crashes or executes arbitrary code.

Blue Team

Detection:

• Monitor for anomalous file uploads with unexpected data types.
• Use WAF rules to block requests with non-standard file objects.
• Implement input validation on all file upload endpoints.

Hunting:

• Search logs for errors related to type confusion or memory corruption.
• Check for unusual process crashes in application logs.

Indicators of Compromise (IOCs)

• Network: HTTP POST requests to /upload with non-file data types.
• File: Log entries containing "TypeError" or "Invalid type" errors.
• System: Unexpected application crashes or high memory usage.
• Registry: NPM packages with similar names to Uppy (typosquatting).

Detection Engineering

YARA Rule

rule CVE_2025_70023_Uppy_TypeConfusion {
    meta:
        description = "Detects potential exploitation of CVE-2025-70023 in Uppy v0.25.6"
        author = "Valters IT"
        date = "2025-04-01"
    strings:
        $s1 = "uppy" nocase
        $s2 = "v0.25.6" nocase
        $s3 = "processFile" nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-70023 Uppy Type Confusion Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects exploitation attempts of CVE-2025-70023 via anomalous file uploads
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/upload'
        cs-uri-query|contains: 'file='
    condition: selection
falsepositives:
    - Legitimate file uploads
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-70023 Uppy Type Confusion Exploit"; flow:to_server; content:"POST"; http_method; content:"/upload"; http_uri; content:"file="; http_client_body; pcre:"/file=[^&]+/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Isolate or disable Uppy v0.25.6 instances until a patch is available.
2. Short-term: Implement strict input validation and type checking on all file upload endpoints.
3. Long-term: Upgrade to a patched version of Uppy once released. Monitor vendor channels for updates.
4. Compensating Controls: Use Web Application Firewalls (WAF) to filter malicious payloads. Enable runtime application self-protection (RASP) if available.

Valters IT
Securing Digital Frontiers

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