pyLoad: Unprotected storage_folder enables arbitrary file write to Flask session store and code execution (Incomplete fix for CVE-2026-33509)

The core of this vulnerability lies in the insufficient restriction of the storagefolder option within pyload-ng's configuration. While a previous fix (CVE-2026-33509) aimed to restrict admin-only options, the storagefolder was inadvertently omitted. An attacker with SETTINGS and ADD permissions can leverage this oversight to redirect downloads to the Flask filesystem session store. By planting a malicious pickle payload as a predictable session file, they can trigger arbitrary code execution upon any subsequent HTTP request containing the corresponding session cookie. This represents a significant escalation of privilege, potentially granting an attacker complete control over the system running pyload-ng.

Organizations and individuals utilizing pyload-ng for download management, particularly those with multiple users and less stringent access controls, are at risk. Shared hosting environments where multiple users share the same pyload-ng instance are especially vulnerable, as an attacker could potentially compromise the entire environment through a single user account.

• python / server:

import os
import pickle

# Check for unusual files in the Flask session directory
session_dir = '/path/to/your/pyload-ng/flask_session'
for filename in os.listdir(session_dir):
    if filename.endswith('.pkl'):
        print(f"Suspicious pickle file found: {session_dir}/{filename}")

• python / server:

# Monitor for unusual processes accessing the Flask session directory
ps aux | grep 'pickle' | grep '/path/to/your/pyload-ng/flask_session'

1. 2026-04-04Disclosure

   disclosure

1. Gereserveerd2026-04-02
2. Gepubliceerd2026-04-04
3. Gewijzigd2026-04-07
4. EPSS bijgewerkt2026-04-15

The primary mitigation for CVE-2026-35464 is to immediately upgrade pyload-ng to version 0.5.0b3.dev96 or later, which includes the necessary fix. If upgrading is not immediately feasible, consider implementing stricter access controls to limit the users who possess SETTINGS and ADD permissions. While not a complete solution, carefully reviewing and restricting user privileges can reduce the attack surface. Monitor the Flask session directory for unexpected files or modifications. There are no specific WAF rules or Sigma/YARA patterns readily available for this specific vulnerability, but general pickle deserialization detection rules may provide some level of protection.