yt-dlp and youtube-dl vulnerable to file system modification and RCE through improper file-extension sanitization

Summary

`yt-dlp` and `youtube-dl` are command-line audio/video downloaders. Prior to the fixed versions, `yt-dlp` and `youtube-dl` do not limit the extensions of downloaded files, which could lead to arbitrary filenames being created in the download folder (and path traversal on Windows). Since `yt-dlp` and `youtube-dl` also read config from the working directory (and on Windows executables will be executed from the `yt-dlp` or `youtube-dl` directory), this could lead to arbitrary code being executed. `yt-dlp` version 2024.07.01 fixes this issue by whitelisting the allowed extensions. `youtube-dl` fixes this issue in commit `d42a222` on the `master` branch and in nightly builds tagged 2024-07-03 or later. This might mean some very uncommon extensions might not get downloaded, however it will also limit the possible exploitation surface. In addition to upgrading, have `.%(ext)s` at the end of the output template and make sure the user trusts the websites that they are downloading from. Also, make sure to never download to a directory within PATH or other sensitive locations like one's user directory, `system32`, or other binaries locations. For users who are not able to upgrade, keep the default output template (`-o "%(title)s [%(id)s].%(ext)s`); make sure the extension of the media to download is a common video/audio/sub/... one; try to avoid the generic extractor; and/or use `--ignore-config --config-location ...` to not load config from common locations.

Timeline

1. Jul 2, 2024, 1:47 PM UTCCVE published
2. Jul 2, 2024, 3:17 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: total

3. Aug 2, 2024, 4:12 AM UTCRecord last updated

Affected versions

• yt-dlp yt-dlp

  fixed in 2024.07.01

• ytdl-org youtube-dl

  From 2015.01.25; From nightly · fixed in d42a222

• yt-dlpPyPI

  fixed in 2024.07.01

References 8