copyparty has DOM-Based XSS vulnerability when displaying multimedia metadata

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.4 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS

• CVE-2025-54423: 0.47% estimated exploitation activity in the next 30 days; percentile 40.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An unauthenticated attacker is able to execute arbitrary JavaScript code in a victim's browser due to improper sanitization of multimedia tags in music files, including m3u files. Details Multimedia metadata is rendered in the web-app without sanitization. This can be exploited in two ways: a user which has the necessary permission for uploading files can upload a song with an artist-name such as <img src=x onerror=alert(document.domain) an unauthenticated user can trick another user into clicking a malicious URL, performing this same exploit using an externally-hosted m3u file The CVE score and PoC is based on the m3u approach, which results in a higher severity. PoC 1. Create a file named song.m3u with the following content. Host this file on an attacker-controlled web server. 2. Craft and share the malicious URL: Impact Any user that accesses this malicious URL is impacted.

Published by the source

28 Jul 2025, 16:41 UTC

Last modified by the source

7 Jul 2026, 17:57 UTC

Source last checked

26 Oct 2026, 13:32 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9q4r-x2hj-jmvr

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9q4r-x2hj-jmvr

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# Patch Next advisory brief: CVE-2025-54423

Advisory: copyparty has DOM-Based XSS vulnerability when displaying multimedia metadata
IDs: CVE-2025-54423, GHSA-9q4r-x2hj-jmvr
Record: https://patchnext.com/advisories/cve-2025-54423 (revision 2, source checked 26 Oct 2026, 13:32 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: copyparty 1.18.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI copyparty: affected <= 1.18.4; fixed in 1.18.5

## Suggested inspection (read-only)
- `python -m pip show copyparty`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on copyparty.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9q4r-x2hj-jmvr (OSV record GHSA-9q4r-x2hj-jmvr lists affected ranges: PyPI copyparty >=0 <1.18.5 (fixed))
- Verified: https://github.com/advisories/GHSA-9q4r-x2hj-jmvr (GitHub-reviewed advisory GHSA-9q4r-x2hj-jmvr lists affected ranges: PyPI copyparty >=0 <=1.18.4)

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