CVE-2025-27145

A DOM-Based XSS was discovered in copyparty, a portable fileserver. The vulnerability is considered low-risk.

Details

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: 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.

Proof of Concept (POC)

1. Create an empty file named <img src=x onerror="alert(1)">
2. Drag-and-drop the file into the browser to initiate an upload
3. The alert(1) is executed

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2025-27145 has a CVSS score of 3.6 (Low). The vector is requires local access, no privileges required, and user interaction required. 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 (1.16.15); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-27145? CVE-2025-27145 is a low-severity cross-site scripting (XSS) vulnerability in copyparty (pip), affecting versions < 1.16.15. It is fixed in 1.16.15. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2025-27145? CVE-2025-27145 has a CVSS score of 3.6 (Low). 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 copyparty are affected by CVE-2025-27145? copyparty (pip) versions < 1.16.15 is affected.
4. Is there a fix for CVE-2025-27145? Yes. CVE-2025-27145 is fixed in 1.16.15. Upgrade to this version or later.
5. Is CVE-2025-27145 exploitable, and should I be worried? Whether CVE-2025-27145 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-2025-27145 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-2025-27145? Upgrade copyparty to 1.16.15 or later.