CVE-2026-26331 PoC — yt-dlp: Arbitrary Command Injection when using the `--netrc-cmd` option

Title:yt-dlp: Arbitrary Command Injection when using the `--netrc-cmd` option (CVE-2026-26331)
Description:yt-dlp is a command-line audio/video downloader. Starting in version 2023.06.21 and prior to version 2026.02.21, when yt-dlp's `--netrc-cmd` command-line option (or `netrc_cmd` Python API parameter) is used, an attacker could achieve arbitrary command injection on the user's system with a maliciously crafted URL. yt-dlp maintainers assume the impact of this vulnerability to be high for anyone who uses `--netrc-cmd` in their command/configuration or `netrc_cmd` in their Python scripts. Even though the maliciously crafted URL itself will look very suspicious to many users, it would be trivial for a maliciously crafted webpage with an inconspicuous URL to covertly exploit this vulnerability via HTTP redirect. Users without `--netrc-cmd` in their arguments or `netrc_cmd` in their scripts are unaffected. No evidence has been found of this exploit being used in the wild. yt-dlp version 2026.02.21 fixes this issue by validating all netrc "machine" values and raising an error upon unexpected input. As a workaround, users who are unable to upgrade should avoid using the `--netrc-cmd` command-line option (or `netrc_cmd` Python API parameter), or they should at least not pass a placeholder (`{}`) in their `--netrc-cmd` argument.

Proof of Concept for an arbitrary command injection vulnerability in yt-dlp’s --netrc-cmd option (GHSA-g3gw-q23r-pgqm / CVE-2026-26331). Demonstrates shell command execution via maliciously crafted URLs in affected versions (≥ 2023.06.21, < 2026.02.21).

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