CVE-2025-27145 copyparty renders unsanitized filenames as HTML when user uploads empty files
An attacker can execute arbitrary JavaScript via maliciously named empty files during drag-and-drop uploads, potentially reading user files.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-27145?
CVE-2025-27145 is a low-severity cross-site scripting vulnerability in 9001 copyparty, published on 25 Feb 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
copyparty, a portable file server, has a DOM-based cross-site scripting vulnerability in versions prior to 1.16.15. The vulnerability is considered low-risk. By handing someone a maliciously-named file, and then tricking them into dragging the file into copyparty's Web-UI, an attacker could execute arbitrary javascript with the same privileges as that user. For example, this could give unintended read-access to files owned by that user. The bug is triggered by the drag-drop action itself; it is not necessary to actually initiate the upload. The file must be empty (zero bytes). Note that, as a general-purpose webserver, it is intentionally possible to upload HTML-files with arbitrary javascript in `<script>` tags, which will execute when the file is opened. The difference is that this vulnerability would trigger execution of javascript during the act of uploading, and not when the uploaded file was opened. Version 1.16.15 contains a fix.
Which versions are affected by CVE-2025-27145?
3 open source packages ship an affected version, including copyparty. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
copyparty PyPI | All versions | 1.16.15 |
copyparty PyPI | All versions | 1.16.15 |
copyparty PyPI | All versions | 1.16.15 |
Products include 9001 Copyparty.
How do I fix CVE-2025-27145?
Upgrade copyparty to 1.16.15 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-27145 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-27145 exists.
Other vulnerabilities in 9001 copyparty
- CVE-2023-41471 Cross-site scripting in n/a
- CVE-2025-54796 Copyparty is vulnerable to Regex Denial of Service (ReDoS) attacks through "Recent Uploads" page
- CVE-2023-37474 Path traversal in copyparty
- CVE-2025-54589 copyparty Reflected XSS via Filter Parameter
- CVE-2023-38501 copyparty vulnerable to reflected cross-site scripting via k304 parameter
Sources
Also known as GHSA-m2jw-cj8v-937r, PYSEC-2026-1278.