CVE-2023-40581

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CVE-2023-40581

Summary: yt-dlp command injection when using `%q` in `--exec` on Windows

Details: yt-dlp is a youtube-dl fork with additional features and fixes. yt-dlp allows the user to provide shell command lines to be executed at various stages in its download steps through the `--exec` flag. This flag allows output template expansion in its argument, so that metadata values may be used in the shell commands. The metadata fields can be combined with the `%q` conversion, which is intended to quote/escape these values so they can be safely passed to the shell. However, the escaping used for `cmd` (the shell used by Python's `subprocess` on Windows) does not properly escape special characters, which can allow for remote code execution if `--exec` is used directly with maliciously crafted remote data. This vulnerability only impacts `yt-dlp` on Windows, and the vulnerability is present regardless of whether `yt-dlp` is run from `cmd` or from `PowerShell`. Support for output template expansion in `--exec`, along with this vulnerable behavior, was added to `yt-dlp` in version 2021.04.11. yt-dlp version 2023.09.24 fixes this issue by properly escaping each special character. `\n` will be replaced by `\r` as no way of escaping it has been found. It is recommended to upgrade yt-dlp to version 2023.09.24 as soon as possible. Also, always be careful when using --exec, because while this specific vulnerability has been patched, using unvalidated input in shell commands is inherently dangerous. For Windows users who are not able to upgrade: 1. Avoid using any output template expansion in --exec other than {} (filepath). 2. If expansion in --exec is needed, verify the fields you are using do not contain ", | or &. 3. Instead of using --exec, write the info json and load the fields from it instead.

References: https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.09.24.003044, https://github.com/yt-dlp/yt-dlp/releases/tag/2021.04.11, https://github.com/yt-dlp/yt-dlp/releases/tag/2023.09.24, https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/40xxx/CVE-2023-40581.json, https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg, https://nvd.nist.gov/vuln/detail/CVE-2023-40581, https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e