CVE-2026-44226: pyLoad Information Disclosure Vulnerability

CVE-2026-44226 Overview

CVE-2026-44226 is an information disclosure vulnerability in pyLoad, a free and open-source download manager written in Python. The pyload-ng WebUI returns full Python tracebacks to clients when unhandled exceptions occur. The /web/<path:filename> route is reachable without authentication and renders attacker-controlled template names. An unauthenticated remote attacker can request a non-existent template to trigger a server exception and receive internal stack traces in the HTTP response. The issue is fixed in version 0.5.0b3.dev100.

Critical Impact
Unauthenticated remote attackers can extract internal Python stack traces, file paths, and runtime details that aid reconnaissance for follow-on attacks.

Affected Products

pyLoad (pyload-ng) WebUI versions prior to 0.5.0b3.dev100
Python-based deployments exposing the pyLoad WebUI to untrusted networks
Self-hosted pyLoad instances with default error handling enabled

Discovery Timeline

2026-05-11 - CVE-2026-44226 published to NVD
2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-44226

Vulnerability Analysis

The vulnerability is classified under [CWE-209]: Generation of Error Message Containing Sensitive Information. The pyload-ng WebUI fails to suppress detailed exception information when rendering templates. When a request triggers an unhandled Python exception, the framework returns the full traceback to the HTTP client instead of a generic error response.

The affected endpoint /web/<path:filename> accepts arbitrary path values as template names without authentication. An attacker can request any non-existent template to deterministically trigger a TemplateNotFound or similar exception. The resulting response exposes internal module paths, function names, library versions, and server-side file system layout.

This information assists attackers in mapping the application's internal structure and identifying additional attack surfaces. While the vulnerability does not directly compromise integrity or availability, it weakens the security posture by providing reconnaissance data to unauthenticated adversaries.

Root Cause

The root cause is missing exception handling combined with an authentication gap on the /web/<path:filename> route. The WebUI propagates raw framework exceptions to the response layer rather than catching them and returning sanitized error pages. Debug-style error reporting remains active in production code paths.

Attack Vector

Exploitation requires only network access to the pyLoad WebUI. The attacker issues an HTTP GET request to /web/ followed by a path that does not correspond to a valid template file. The server processes the request, fails to locate the template, and returns the Python traceback in the HTTP response body. No credentials, user interaction, or special tooling are required.

The vulnerability is described in the GitHub Security Advisory GHSA-c3gc-9pf2-84gg.

Detection Methods for CVE-2026-44226

Indicators of Compromise

HTTP requests to /web/<path:filename> with non-standard or randomized filename values from unauthenticated sources
WebUI access logs containing 500-level responses correlated with template lookup errors
Outbound responses containing Python traceback strings such as Traceback (most recent call last) originating from the pyLoad service

Detection Strategies

Inspect pyLoad WebUI access logs for repeated 500 errors on the /web/ path, especially from external IP addresses
Deploy web application firewall rules to identify response bodies containing Python traceback signatures leaving the server
Hunt for reconnaissance patterns where multiple unique template names are requested in a short timeframe from a single source

Monitoring Recommendations

Forward pyLoad application and access logs to a centralized SIEM for analysis and long-term retention
Alert on any HTTP 500 response from the WebUI returning more than a threshold size, indicating verbose error output
Track the pyLoad version in asset inventories and flag instances running builds older than 0.5.0b3.dev100

How to Mitigate CVE-2026-44226

Immediate Actions Required

Upgrade pyLoad to version 0.5.0b3.dev100 or later on all production and development instances
Restrict network exposure of the pyLoad WebUI to trusted networks or VPN access only
Place the WebUI behind a reverse proxy that rewrites 5xx responses to sanitized error pages

Patch Information

The vulnerability is fixed in pyLoad version 0.5.0b3.dev100. The patched release suppresses raw traceback output on the /web/<path:filename> route and returns generic error responses to unauthenticated clients. Refer to the pyLoad Security Advisory GHSA-c3gc-9pf2-84gg for the upstream fix details.

Workarounds

Configure a reverse proxy such as Nginx or Caddy to intercept and replace 5xx responses from the pyLoad backend
Add authentication enforcement at the proxy layer to block unauthenticated access to the /web/ path
Disable debug or verbose error reporting in any custom pyLoad deployment configuration

bash

# Example Nginx reverse proxy snippet to suppress traceback leakage
location /web/ {
    proxy_pass http://127.0.0.1:8000;
    proxy_intercept_errors on;
    error_page 500 502 503 504 /custom_error.html;
}