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Pyload NgApplication · Pyload Ng Project

CVE-2026-33511

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-24
Fix available
A fix is available. Upgrade to 0.5.0b3.dev97 or later.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
pyLoad is a free and open-source download manager written in Python. From version 0.4.20 to before version 0.5.0b3.dev97, the local_check decorator in pyLoad's ClickNLoad feature can be bypassed by any remote attacker through HTTP Host header spoofing. This allows unauthenticated remote users to access localhost-restricted endpoints, enabling them to inject arbitrary downloads, write files to the storage directory, and execute JavaScript code. This issue has been patched in version 0.5.0b3.dev97.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

pyLoad's local_check decorator, designed to restrict certain endpoints to localhost access, can be bypassed by remote attackers through HTTP Host header spoofing. This enables unauthenticated remote users to access localhost-restricted endpoints, allowing injection of arbitrary downloads, file writes to the storage directory, and JavaScript code execution.

MitigationUpgrade pyLoad to version 0.5.0b3.dev97 or later to apply the patch that addresses the Host header spoofing bypass vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Pyload NgApplication
Affected:>= 0.5.0a5.dev528, < 0.5.0b3.dev97
PyloadApplication
Affected:<= 0.4.20

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify pyLoad version
    Locate and read the version file or check the package metadata. Common locations include: pyload/__init__.py, setup.py, version info in the package, or the web interface version display at /api/get_version
    Affected if version is 0.5.0a5.dev528 or higher but lower than 0.5.0b3.dev97, OR version is 0.4.20 or lower (legacy pyLoad)
  2. Verify network exposure
    Check the configuration or running process to determine what network interfaces pyLoad binds to. Look for binding to 0.0.0.0 or external IP addresses rather than 127.0.0.1 only
    Affected if pyLoad is accessible from non-localhost network interfaces (not bound to 127.0.0.1 only)
  3. Check if Host header validation exists in local_check
    Inspect the source code of the local_check decorator function, typically found in the pyload core module. Look for explicit validation that compares the Host header value against expected localhost values
    Affected if the local_check decorator does not validate the Host header and relies solely on the source IP being localhost

A user is affected if their pyLoad version falls within the vulnerable ranges AND the service is accessible from remote hosts, allowing attackers to spoof the Host header to bypass localhost restrictions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.5.0b3.dev97 or later
Fixed in 0.5.0b3.dev97
Interim mitigation

Upgrade pyLoad to version 0.5.0b3.dev97 or later to apply the patch that addresses the Host header spoofing bypass vulnerability.

Recommended fix High confidence

pyLoad 0.5.0b3.dev97 or later (pyload-ng)

  1. 1. Identify the currently installed pyLoad version using your package manager or the web interface
  2. 2. Stop the pyLoad service
  3. 3. Upgrade pyLoad to version 0.5.0b3.dev97 or later using your package manager (pip install --upgrade pyload-ng, or your distribution's package manager)
  4. 4. Verify the new version is installed: pip show pyload-ng or check the web interface
  5. 5. Restart the pyLoad service
  6. 6. Test that the ClickNLoad functionality still works correctly after the upgrade
Caveat Moving from pyLoad 0.4.x to 0.5.x may introduce breaking changes; review release notes before upgrading in production environments

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Pyload Ng Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,570
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33511 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data