CVE-2025-24891: Dumb Drop Path Traversal Vulnerability

CVE-2025-24891 Overview

CVE-2025-24891 is a critical path traversal vulnerability discovered in Dumb Drop, a file upload application. Users with permission to upload to the service can exploit this vulnerability to overwrite arbitrary system files. Since the container runs as root by default, attackers face no limitations on what files can be overwritten. This enables injection of malicious payloads into files executed on schedule or upon certain service actions. Because the service does not require authentication by default, this vulnerability may permit wholly unprivileged users to gain root access. Otherwise, any user with a PIN can exploit this flaw.

Critical Impact

Unauthenticated attackers can achieve root-level system compromise by exploiting the path traversal vulnerability to overwrite critical system files, potentially leading to complete container takeover.

Affected Products

• Dumb Drop (versions prior to security patch)

Discovery Timeline

• 2025-01-31 - CVE CVE-2025-24891 published to NVD
• 2025-01-31 - Last updated in NVD database

Technical Details for CVE-2025-24891

Vulnerability Analysis

This path traversal vulnerability (CWE-22) exists in the file upload functionality of Dumb Drop. The application fails to properly sanitize user-supplied filenames during the upload initialization process, allowing attackers to use directory traversal sequences (such as ../) to navigate outside the intended upload directory and write files to arbitrary locations on the filesystem.

The vulnerability is particularly severe due to the application's default configuration. The Docker container runs with root privileges, meaning successful exploitation grants full control over the entire container filesystem. Additionally, authentication is optional, potentially allowing completely unauthenticated access to the vulnerable upload endpoint.

Root Cause

The root cause of this vulnerability is insufficient input validation in the /upload/init endpoint. The application did not properly sanitize the filename parameter in incoming upload requests, allowing directory traversal sequences to be processed without restriction. This enabled attackers to craft malicious filenames that would write files outside the designated upload directory.

Attack Vector

The attack is network-accessible and requires user interaction. An attacker can exploit this vulnerability by sending a specially crafted POST request to the /upload/init endpoint containing a malicious filename with path traversal sequences. By targeting sensitive files such as cron jobs, startup scripts, or other executable files, an attacker can achieve arbitrary code execution with root privileges when those files are subsequently executed by the system.

// Security patch applied in server.js
// Source: https://github.com/DumbWareio/DumbDrop/commit/cb586316648ccbfb21d27b84e90d72ccead9819d

 // Routes
 app.post('/upload/init', async (req, res) => {
     const { filename, fileSize } = req.body;

    const safeFilename = path.normalize(filename).replace(/^(\.\.(\\/|\\|$))+/, '')
     
     // Check file size limit
     if (fileSize > maxFileSize) {

The patch introduces proper filename sanitization using path.normalize() combined with a regex pattern to strip leading directory traversal sequences, preventing attackers from escaping the upload directory.

Detection Methods for CVE-2025-24891

Indicators of Compromise

• Unexpected file modifications in system directories outside the designated upload path
• Files containing malicious payloads appearing in /etc/cron.d/, /etc/cron.daily/, or other scheduled task directories
• Unusual POST requests to the /upload/init endpoint with filenames containing ../ sequences
• Evidence of unauthorized script execution or persistence mechanisms in the container

Detection Strategies

• Monitor HTTP request logs for path traversal patterns in filename parameters (e.g., ../, ..%2f, ..%5c)
• Implement file integrity monitoring on critical system directories within containers running Dumb Drop
• Deploy web application firewall (WAF) rules to detect and block path traversal attempts
• Review container logs for unexpected file write operations outside the upload directory

Monitoring Recommendations

• Enable detailed logging for all file upload operations in Dumb Drop
• Configure alerting for any file modifications in sensitive system directories
• Implement runtime container security monitoring to detect privilege escalation attempts
• Monitor for unexpected cron job additions or modifications within the container environment

How to Mitigate CVE-2025-24891

Immediate Actions Required

• Update Dumb Drop to the latest version that includes the security patch (commit cb586316648ccbfb21d27b84e90d72ccead9819d or later)
• Enable authentication (PIN) on all Dumb Drop instances to restrict upload access
• Configure the container to run as a non-root user to limit the impact of potential exploitation
• Review recent uploads and system files for signs of compromise

Patch Information

The vulnerability has been addressed in the official Dumb Drop repository. The security patch implements proper filename sanitization by normalizing the path and stripping directory traversal sequences before processing uploads. Organizations should apply this patch immediately by pulling the latest version from the DumbWareio/DumbDrop GitHub repository. For detailed technical information, refer to the GitHub Security Advisory GHSA-24f2-fv38-3274.

Workarounds

• Enable authentication by configuring a PIN for the Dumb Drop service
• Run the Dumb Drop container with a non-root user by adding user: "1000:1000" to your Docker configuration
• Mount the upload directory with restricted permissions and as a separate volume
• Deploy a reverse proxy with path traversal filtering in front of the Dumb Drop service

# Configuration example - Running Dumb Drop as non-root user in Docker Compose
services:
  dumbdrop:
    image: dumbwareio/dumbdrop:latest
    user: "1000:1000"
    environment:
      - DUMBDROP_PIN=your_secure_pin_here
    volumes:
      - ./uploads:/app/uploads:rw
    read_only: true