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PYSEC-2026-1822
No affected components available
Summary
Any unauthenticated attacker can bypass the localhost restrictions posed by the application and utilize this to create arbitrary packages.
Details
Any unauthenticated attacker can bypass the localhost restrictions posed by the application and utilize this to create arbitrary packages. This is done by changing the Host header to the value of 127.0.0.1:9666.
PoC
The application has middleware that prevents access to several routes by checking whether the Host header has a specific value. We bypassed this restriction.
https://github.com/pyload/pyload/blob/4159a1191ec4fe6d927e57a9c4bb8f54e16c381d/src/pyload/webui/app/blueprints/cnl_blueprint.py#L21-L36
#: decorator
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
Below we see that the '/flash/add' endpoint uses the middleware above.
https://github.com/pyload/pyload/blob/4159a1191ec4fe6d927e57a9c4bb8f54e16c381d/src/pyload/webui/app/blueprints/cnl_blueprint.py#L56-L58C11
@bp.route("/flash/add", methods=["POST"], endpoint="add")
@local_check
def add():
Notice how we are not authorized to access this endpoint when sending a request.
However, if we set the Host header to be 127.0.0.1:9666, we notice the request returns success.
Checking the front end as an admin, we now see that this did indeed succeed.
Impact
An unauthenticated user can perform actions that should only be available to authenticated users.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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