CVE-2024-38519High· 7.8▾ Twilightyt-dlp File system modification and RCE through improper file-extension sanitization
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 42.9 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
0.3%
0.3% → 0.3%
yt-dlp does 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 also reads config from the working directory (and on Windows executables will be executed from the yt-dlp directory) this could lead to arbitrary code being executed.
yt-dlp version 2024.07.01 fixes this issue by whitelisting the allowed extensions.
This means some very uncommon extensions might not get downloaded; however, it will also limit the possible exploitation surface.
It is recommended to upgrade yt-dlp to version 2024.07.01 as soon as possible, always have .%(ext)s at the end of the output template, and make sure you trust the websites that you are downloading from. Also, make sure to never download to a directory within PATH or other sensitive locations like your user directory, system32, or other binaries locations.
For users not able to upgrade:
--ies default,-generic)-o "%(title)s [%(id)s].%(ext)s)--write-subs, --write-auto-subs, --all-subs, --write-srt)--ignore-config --config-location ... to not load config from common locationsOne potential exploitation might look like this:
From a mimetype we do not know, we default to trimming the leading bit and using the remainder. Given a webpage that contains
<script type="application/ld+json">
{
"@context": "https://schema.org",
"@type": "VideoObject",
"name": "ffmpeg",
"encodingFormat": "video/exe",
"contentUrl": "https://example.com/video.mp4"
}
</script>
this will try and download a file called ffmpeg.exe (-o "%(title)s.%(ext)s).
ffmpeg.exe will be searched for in the current directory, and so upon the next run arbitrary code can be executed.
Alternatively, when engineering a file called yt-dlp.conf to be created, the config file could contain --exec ... and so would also execute arbitrary code.
A big thanks to @JarLob for independently finding a new application of the same underlying issue. More can be read about on the dedicated GitHub Security Lab disclosure here: Path traversal saving subtitles (GHSL-2024-090)
yt-dlp < 2024.07.01Upgrade to a patched release:
yt-dlp 2024.07.01Connected by shared product, vendor, weakness, or advisory.
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