# CVE-2026-109966: yt-dlp-web-ui through 4.0.0 Argument Injection via Service.Formats JSON-RPC Method

> Unauthenticated attackers can inject yt-dlp options to read arbitrary server files or potentially execute code via the JSON-RPC interface.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** GHSA-g8v9-4g6m-3vc9

## What is CVE-2026-109966?

CVE-2026-109966 is a medium-severity command injection vulnerability in marcopiovanello yt-dlp-web-ui, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

yt-dlp-web-ui through 4.0.0 contains an argument injection vulnerability that allows unauthenticated remote attackers to inject yt-dlp options by supplying a dash-prefixed url parameter to the Service.Formats JSON-RPC method. Attackers can send values like --load-info-json via /rpc/http or /rpc/ws to make yt-dlp load attacker-chosen JSON files from the server filesystem, with contents reflected in responses.

Weakness: CWE-88 (Improper Neutralization of Argument Delimiters in a Command)

## Which versions are affected by CVE-2026-109966?


## How do I fix CVE-2026-109966?

No fix has been published for CVE-2026-109966 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-109966 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109966 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-109966 and fix it if it is affected.

What it is: CVE-2026-109966 is a medium-severity command injection vulnerability in marcopiovanello yt-dlp-web-ui, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-109966 exists.

Affected product: marcopiovanello yt-dlp-web-ui. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-109966/ (Markdown: https://insights.sbomify.com/CVE-2026-109966/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-109966
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-109966
- OSV: https://osv.dev/vulnerability/CVE-2026-109966

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-109966/
Summaries are generated and may contain mistakes; the official description above is the record.