# CVE-2026-109966: yt-dlp-web-ui argument injection in JSON-RPC methods

Source: https://junglewise.ai/threats/cve-2026-109966-yt-dlp-web-ui-through-4-0-0-contains-an-argument-injection  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-109966 · Severity: medium · CVSS 5.3 · Published 2026-10-13

yt-dlp-web-ui is a web interface and RPC server for yt-dlp, a video downloader tool. An unauthenticated attacker can inject command-line arguments through the Service.Formats RPC method, allowing them to read arbitrary files from the server filesystem. This could expose sensitive configuration or private data stored on the system.

Technologies: [Marcopiovanello Yt-Dlp-Web-Ui](https://junglewise.ai/threats/technologies/yt-dlp-web-ui). Vendors: [Marcopiovanello](https://junglewise.ai/threats/vendors/marcopiovanello).

## Quick answers

**Is CVE-2026-109966 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109966 being exploited in the wild.

**How severe is CVE-2026-109966?** Medium severity, with a CVSS score of 5.3, published 13 October 2026.

**Which products and versions are affected?** Marcopiovanello Yt-Dlp-Web-Ui through 4.0.0.

**Is there a fix for CVE-2026-109966?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-109966 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-109966?** Check whether you run Marcopiovanello Yt-Dlp-Web-Ui at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an argument injection flaw in the JSON-RPC endpoint where URL parameters prefixed with dashes (e.g., --load-info-json) are passed unsanitized to the underlying yt-dlp command execution. An attacker can craft malicious requests to /rpc/http or /rpc/ws with dash-prefixed parameters that cause yt-dlp to load and process attacker-specified JSON files from the server filesystem, with the contents reflected in responses. The flaw is accessible without authentication.

## Affected products

- marcopiovanello yt-dlp-web-ui through 4.0.0

## Timeline

- 2026-10-13: disclosed

## References

- [https://github.com/marcopiovanello/yt-dlp-web-ui](https://github.com/marcopiovanello/yt-dlp-web-ui)
- [https://github.com/marcopiovanello/yt-dlp-web-ui/blob/v4.0.0/server/formats/parser.go](https://github.com/marcopiovanello/yt-dlp-web-ui/blob/v4.0.0/server/formats/parser.go)

## Related threats

- [yt-dlp-web-ui NULL pointer dereference in Service.Formats method](https://junglewise.ai/threats/cve-2026-109967-yt-dlp-web-ui-through-4-0-0-contains-a-null-pointer-dereference)
- [marcopiovanello yt-dlp-web-ui command injection in NewGenericDownload](https://junglewise.ai/threats/cve-2026-93371-marcopiovanello-yt-dlp-web-ui-command-injection-in)