CVE-2023-40581: yt-dlp command injection when using `%q` in `--exec` on Windows
Impact yt-dlp allows the user to provide shell commands to be executed at various stages in its download process through the --exec flag. This flag allows output template expansion in its argument, so that video 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) did 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.
shell yt-dlp https://youtu.be/Jo66yyCpHcQ --exec "echo %(title)q" [youtube] Extracting URL: https://youtu.be/Jo66yyCpHcQ [youtube] Jo66yyCpHcQ: Downloading webpage [youtube] Jo66yyCpHcQ: Downloading ios player API JSON [youtube] Jo66yyCpHcQ: Downloading android player API JSON [youtube] Jo66yyCpHcQ: Downloading m3u8 information [info] Jo66yyCpHcQ: Downloading 1 format(s): 135+251 [download] Destination: ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f135.mp4 [download] 100% of 4.85KiB in 00:00:00 at 60.20KiB/s [download] Destination: ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f251.webm [download] 100% of 4.80KiB in 00:00:00 at 31.58KiB/s [Merger] Merging formats into "＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].mkv" Deleting original file ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f135.mp4 (pass -k to keep) Deleting original file ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f251.webm (pass -k to keep) [Exec] Executing command: echo "\"&echo(&echo(pwned&rem(" "\"
pwned
Patches 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.
Workarounds 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: - Avoid using any output template expansion in --exec other than {} (filepath). - If expansion in --exec is needed, verify the fields you are using do not contain ", | or &. - Instead of using --exec, write the info json and load the fields from it instead.
References - 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/releases/tag/2023.09.24 - https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.09.24.003044 - https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e
Other sources
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.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the vulnerability ID for this advisory?
The vulnerability ID for this advisory is CVE-2023-40581.
What is the severity of CVE-2023-40581?
The severity of CVE-2023-40581 is high with a CVSS score of 8.3 (out of 10).
What is the impact of CVE-2023-40581?
CVE-2023-40581 allows shell commands to be executed during the download process of `yt-dlp` with potential for command injection.
How can I fix CVE-2023-40581?
To fix CVE-2023-40581, upgrade your `yt-dlp` package to version 2023.09.24 or later using pip.
Where can I find more information about CVE-2023-40581?
You can find more information about CVE-2023-40581 in the official GitHub security advisory and the associated references.