GHSA-f7j3-774f-rfhj yt-dlp: File Downloader cookie leak with curl

• PyPI yt-dlp: >= 2023.9.24, < 2026.6.9 → fixed in 2026.6.9

Summary If curl is used an external downloader for yt-dlp, cookies may be leaked to an unintended host upon HTTP redirect or when the host for download fragments differs from their parent manifest's. This is the equivalent to GHSA-v8mc-9377-rwjj for the `curl` downloader. The vulnerable behavior is present in yt-dlp released since 2023.09.24. Details At the file download stage, the cookies are passed by yt-dlp to the file downloader via `--cookie`. However, unless these are loaded from a file, this operation does not activate the cookie engine. As a result, `curl` will send cookies with requests to domains or paths for which the cookies are not scoped. An example of a potential attack scenario exploiting this vulnerability: 1. an attacker has crafted a malicious website with an embedded URL designed to be detected by yt-dlp as a video download. This embedded URL has the domain of a trusted site that the user has loaded cookies for, and conducts an unvalidated redirect to a target URL. 2. yt-dlp extracts this URL and calculates the cookies which are then passed to `curl`. 3. the download URL redirects to a server controlled by the attacker, to which `curl` forwards the user's sensitive cookie information. Patches yt-dlp version 2026.06.09 fixes this issue by doing the following: • Pass the cookies through stdin via `--cookie -` if `curl` is version 7.59 or higher. • Pass the cookies via `--cookie /dev/fd/0` if the system supports this device file. • In all other cases create a temporary file, save the cookies and then pass via `--cookie `. Workarounds It is recommended to upgrade yt-dlp to version 2026.06.09 as soon as possible. For users who are not able to upgrade: • Do not use `--downloader curl`.