Affected: yt-dlp

yt-dlp is a command-line audio/video downloader. Prior to 2026.06.09, if aria2c is used as an external downloader for a fragmented manifest format (such as an HLS/DASH stream), yt-dlp passes insufficiently sanitized input to aria2c that allows an attacker to perform an arbitrary file write. On Windows platforms, this can lead to immediate arbitrary code execution. On non-Windows platforms, this can lead to arbitrary code execution upon the next invocation of yt-dlp. This vulnerability is fixed in 2026.06.09.

Affected: PyPI: yt-dlp

### Summary If aria2c is used as an external downloader for a fragmented manifest format (such as an HLS/DASH stream), yt-dlp passes insufficiently sanitized input to aria2c that allows an attacker to perform an arbitrary file write. On Windows platforms, this can lead to immediate arbitrary code execution. On non-Windows platforms, this can lead to arbitrary code execution upon the next invocation of yt-dlp.

### Details When downloading a fragmented manifest format such as an HLS or DASH stream, yt-dlp first extracts a list of all fragment URLs from the stream's manifest. If the user has selected aria2c as an external downloader, yt-dlp then constructs an input file for aria2c from the fragment URL list and passes its filepath as the argument to aria2c's `-i` option.

aria2c's `-i` (or `--input-file`) option allows for downloading a list of URIs from the given text file. The text file must be formatted as a list of URIs separated by newlines. aria2c's format permits configuration lines for each URI, which can contain command-line options to be given to aria2c. These optional lines follow each URI line and are signified only by leading whitespace. yt-dlp constructs the input file with these optional lines so that it's able to specify the output filename for each fragment using the `out=` option.

yt-dlp's utilization of the aria2c input file format presents two known attack vectors:

1. An attacker can craft a malicious DASH manifest with one or more fragment URLs that cont…

Affected: PyPI: yt-dlp

### Summary If aria2c is used as an external downloader for a fragmented manifest format (such as an HLS/DASH stream), yt-dlp passes insufficiently sanitized input to aria2c that allows an attacker to perform an arbitrary file write. On Windows platforms, this can lead to immediate arbitrary code execution. On non-Windows platforms, this can lead to arbitrary code execution upon the next invocation of yt-dlp.

### Details When downloading a fragmented manifest format such as an HLS or DASH stream, yt-dlp first extracts a list of all fragment URLs from the stream's manifest. If the user has selected aria2c as an external downloader, yt-dlp then constructs an input file for aria2c from the fragment URL list and passes its filepath as the argument to aria2c's `-i` option.

aria2c's `-i` (or `--input-file`) option allows for downloading a list of URIs from the given text file. The text file must be formatted as a list of URIs separated by newlines. aria2c's format permits configuration lines for each URI, which can contain command-line options to be given to aria2c. These optional lines follow each URI line and are signified only by leading whitespace. yt-dlp constructs the input file with these optional lines so that it's able to specify the output filename for each fragment using the `out=` option.

yt-dlp's utilization of the aria2c input file format presents two known attack vectors:

1. An attacker can craft a malicious DASH manifest with one or more fragment URLs that cont…