CVE-2025-0187: Gradio File Upload DoS Vulnerability

CVE-2025-0187 Overview

CVE-2025-0187 is a Denial of Service (DoS) vulnerability in the file upload feature of gradio-app/gradio version 0.39.1. The flaw stems from improper handling of form-data containing an excessively large filename in file upload requests. Attackers can send a crafted multipart request with an oversized filename field, causing the server to consume resources processing the input. The result is server unresponsiveness and unavailability for legitimate users. Gradio is widely used to expose machine learning models through interactive web interfaces, making this vulnerability relevant to AI/ML deployments. The weakness is classified under [CWE-400: Uncontrolled Resource Consumption].

Critical Impact

Unauthenticated remote attackers can render Gradio applications unresponsive by sending a single crafted file upload request with an oversized filename.

Affected Products

• gradio-app/gradio version 0.39.1 (Python package)
• Applications exposing the Gradio file upload component
• Machine learning demos and interfaces built on the affected Gradio release

Discovery Timeline

• 2025-03-20 - CVE-2025-0187 published to the National Vulnerability Database (NVD)
• 2025-08-01 - Last updated in NVD database

Technical Details for CVE-2025-0187

Vulnerability Analysis

The vulnerability resides in the multipart form-data parsing logic that handles file uploads in Gradio 0.39.1. When a client submits a file upload request, the server reads the filename parameter from the Content-Disposition header. The implementation does not enforce a maximum length on this field before processing. An attacker can supply a filename containing millions of characters, forcing the server to allocate memory and perform string operations against the oversized input. This causes thread blocking and exhausts available worker capacity. Because the Gradio server is typically single-process and serves both the UI and inference endpoints, a single malicious request can disrupt all clients connected to the application.

Root Cause

The root cause is missing input validation on the filename field of multipart upload requests. Gradio accepts arbitrarily large filename strings without enforcing length bounds, byte limits, or early request termination. This violates secure input handling practices for HTTP-facing services and maps directly to [CWE-400] uncontrolled resource consumption.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker only needs reachability to the Gradio HTTP endpoint exposing the file upload route. The exploit consists of issuing a standard HTTP POST request with multipart/form-data content type, where the filename attribute in the Content-Disposition header carries an oversized string payload. Repeated requests amplify the impact and can keep the service offline indefinitely.

No verified exploit code has been published for CVE-2025-0187. Technical details are available in the Huntr Bug Bounty Report.

Detection Methods for CVE-2025-0187

Indicators of Compromise

• HTTP POST requests to Gradio upload endpoints containing Content-Disposition headers with abnormally long filename values (tens of thousands of characters or more).
• Sudden spikes in memory consumption or worker thread saturation on the Gradio process coinciding with inbound upload traffic.
• Application logs showing dropped or timed-out requests immediately following large multipart submissions.

Detection Strategies

• Inspect web server and reverse proxy access logs for multipart upload requests exceeding expected header sizes.
• Deploy Web Application Firewall (WAF) rules that enforce maximum length on the filename attribute of multipart requests.
• Correlate process resource metrics with HTTP request telemetry to identify single requests that trigger disproportionate CPU or memory usage.

Monitoring Recommendations

• Alert on Gradio process unresponsiveness or restarts following abnormal HTTP request patterns.
• Track 4xx and 5xx response rates on upload endpoints as a signal of attempted exploitation.
• Capture full HTTP request headers for forensic review when DoS conditions are detected.

How to Mitigate CVE-2025-0187

Immediate Actions Required

• Upgrade gradio to a version newer than 0.39.1 that addresses the filename handling defect.
• Restrict network exposure of Gradio applications to trusted users via authentication, VPN, or IP allowlists.
• Place Gradio behind a reverse proxy (such as nginx) configured with strict request size and header length limits.

Patch Information

Review the Huntr Bug Bounty Report for remediation guidance and consult the official gradio-app/gradio release notes for the fixed version. Upgrade using pip install --upgrade gradio in affected environments.

Workarounds

• Configure an upstream reverse proxy to reject multipart requests with Content-Disposition headers exceeding a safe length (for example, 1024 bytes).
• Apply rate limiting on the file upload endpoint to reduce the impact of repeated malicious requests.
• Disable the file upload component in Gradio applications that do not require it.

# Example nginx configuration to limit request header and body size
http {
    client_max_body_size 10m;
    large_client_header_buffers 4 8k;
    client_header_buffer_size 1k;

    server {
        location /upload {
            limit_req zone=upload_limit burst=5 nodelay;
            proxy_pass http://gradio_backend;
        }
    }
}