Sign in
Deutsch English Español Polski
Medium

pyLoad Has Incomplete Fix for CVE-2026-33509 -storage_folder Bypass via Session Directory in pyLoad

  • Disclosed: 14.05.2026
  • Updated: 11.10.2026 14:18

Summary

The fix for CVE-2026-33509 prevents setting storage_folder inside PKGDIR or userdir, but does NOT protect the Flask session directory (/tmp/pyLoad/flask). An authenticated attacker can set storage_folder to the session directory and download session files of other users via /files/get/, leading to account takeover.

Details

The fix in src/pyload/core/api/__init__.py:

python
directories = [PKGDIR, userdir]
if any(directories[0].startswith(d) for d in directories[1:]):
    return  # blocked

But the Flask session directory is:

python
session_storage_path = os.path.join(api.get_cachedir(), "flask")
# = /tmp/pyLoad/flask  ← NOT blocked by fix

Attack Chain

  1. Attacker (admin) sets storage_folder = /tmp/pyLoad/flask
  2. Fix does NOT block this — /tmp/pyLoad/flask not inside PKGDIR or userdir
  3. Attacker requests GET /files/get/<victim_session_filename>
  4. send_from_directory('/tmp/pyLoad/flask', session_file) serves victim's session
  5. Attacker uses stolen session → Account Takeover

PoC

<img width="592" height="408" alt="POC" src="https://github.com/user-attachments/assets/936b9f56-325b-437d-9edd-e0d5bb995187" />
python
import os

PKGDIR = "/usr/lib/python3/dist-packages/pyload"
userdir = os.path.expanduser("~/.pyload")
session_dir = "/tmp/pyLoad/flask"

correct_case = lambda x: x
directories = [
    correct_case(os.path.join(os.path.realpath(d), ""))
    for d in [session_dir, PKGDIR, userdir]
]
blocked = any(directories[0].startswith(d) for d in directories[1:])

print(f"Fix blocks session_dir: {blocked}")
# Output: Fix blocks session_dir: False  ← BYPASS CONFIRMED

Impact

Authenticated admin can steal sessions of other users → Account Takeover.

Suggested Fix

python
blocked_dirs = [PKGDIR, userdir, api.get_cachedir()]
directories = [
    os.path.join(os.path.realpath(d), "")
    for d in [value] + blocked_dirs
]
if any(directories[0].startswith(d) for d in directories[1:]):
    return

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) pyload-ng <= 0.5.0b3.dev99 no fix

References

CVSS score 6.5/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
Weakness (CWE)
CWE-706
Platform
Python (PyPI)
Package
pyload-ng
Disclosed
14.05.2026
Updated
11.10.2026 14:18

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2026-2998 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-w727-595x-pc3r - CC BY 4.0

Vulnerability history: pyload-ng

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (58) in the archive
Total entries
58
First → latest
01.2023 10.2026
Without a fix
24
Exploited in attacks
0

Severity breakdown

  • Critical 9
  • High 23
  • Medium 25
  • Low 1

Disclosures per year

Severity:
  1. pyload-ng: getUserData/get_userdata exposed at Perms.ANY allow any authenticated account to brute-force the administrator password
    High · 8.1 ghsa-68w4-83fh-f2w8 >= 0.5.0b3.dev1, <= 0.5.0b3.dev101 no fix
  2. pyLoad: Privilege revocation and password change through the REST API do not invalidate the user's session
    High · 7.5 ghsa-jq7h-wrvp-3rgx <= 0.5.0b3.dev101 no fix
  3. pyLoad: Api.set_user_permission never invalidates the target's session
    High · 7.5 ghsa-889w-m37p-88m5 >= 0.5.0b3.dev98, <= 0.5.0b3.dev101 no fix
  4. pyLoad: Tar extraction creates device nodes and FIFOs (member types not filtered; tarfile extractall without filter=)
    High ghsa-fr26-jjhm-638c <= 0.5.0b3.dev101 no fix
  5. pyLoad has an authentication bypass in API key validation (check_apikey cache)
    High · 8.1 ghsa-r44w-v6gf-x3p6 < 0.5.0b3.dev101 0.5.0b3.dev101
  6. pyLoad is vulnerable to stored XSS in Downloads view via unsanitized link URL in packages.js template literal
    High · 8.7 CVE-2026-45348 <= 0.5.0b3.dev99 no fix
  7. pyLoad Has Incomplete Fix for CVE-2026-33509 -storage_folder Bypass via Session Directory in pyLoad this entry
    Medium · 6.5 CVE-2026-45306 <= 0.5.0b3.dev99 no fix
  8. PyLoad vulnerable to Path Traversal via Package Folder Name in set_package_data
    High · 8.1 CVE-2026-42315 < 0.5.0b3.dev100 0.5.0b3.dev100
  9. pyload-ng: non-admin SETTINGS users can redirect all outbound traffic through an attacker-controlled proxy via unrestricted `proxy.*` config (incomplete fix for CVE-2026-33509 / -35463 / -35464 / -35586)
    High · 8.3 CVE-2026-42313 < 0.5.0b3.dev100 0.5.0b3.dev100
  10. pyLoad has Stale Session Privilege After Role/Permission Change (Privilege Revocation Bypass)
    High · 8.8 CVE-2026-41133 <= 0.5.0b3.dev97 no fix
  11. pyLoad: Unprotected storage_folder enables arbitrary file write to Flask session store and code execution (Incomplete fix for CVE-2026-33509)
    High · 7.5 CVE-2026-35464 <= 0.5.0b3 no fix
  12. pyLoad: Improper Neutralization of Special Elements used in an OS Command
    High · 8.8 CVE-2026-35463 <= 0.5.0b3.dev96 no fix
  13. pyLoad: SSRF filter bypass via HTTP redirect in BaseDownloader (Incomplete fix for CVE-2026-33992)
    Critical CVE-2026-35459 <= 0.5.0b3.dev96 no fix
  14. pyLoad: SSRF in parse_urls API endpoint via unvalidated URL parameter
    High · 7.7 CVE-2026-35187 <= 0.5.0b3.dev96 no fix
  15. pyLoad: Server-Side Request Forgery via Download Link Submission Enables Cloud Metadata Exfiltration
    Critical CVE-2026-33992 <= 0.5.0b3.dev96 no fix
  16. pyLoad SETTINGS Permission Users Can Achieve Remote Code Execution via Unrestricted Reconnect Script Configuration
    High · 7.5 CVE-2026-33509 >= 0.4.0, <= 0.5.0b3.dev96 no fix
  17. pyLoad has an Arbitrary File Write via Path Traversal in edit_package()
    High · 7.1 CVE-2026-29778 >= 0.5.0b3.dev13, < 0.5.0b3.dev97 0.5.0b3.dev97
  18. pyLoad CNL and captcha handlers allow Code Injection via unsanitized parameters
    High · 8.1 CVE-2025-61773 < 0.5.0b3.dev91 0.5.0b3.dev91
  19. Denial-of-Service attack in pyLoad CNL Blueprint using dukpy.evaljs
    High CVE-2025-57751 < 0.5.0b3.dev92 0.5.0b3.dev92
  20. PyLoad vulnerable to SQL Injection via API /json/add_package in add_links parameter
    High CVE-2025-55156 < 0.5.0b3.dev91 0.5.0b3.dev91
Show more (13) Showing 20 of 33

Know which vulnerabilities affect your application

With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.

Connect your application
DockRay newsletter

Application security in your inbox

Important vulnerabilities, actionable guidance and practical advice for your applications. Choose your technologies and follow what matters to your project.

  • A daily digest of new vulnerabilities, critical ones included.
  • Notifications about important updates.
  • Practical advice on application security and monitoring.

Leave empty to receive updates for every technology.

Privacy policy

Free to subscribe. Unsubscribe with one click in any email.