CVE-2024-22423 (Python, published 2024-04-09T18:15Z)
Description: value: yt-dlp is a youtube-dl fork with additional features and fixes. The patch that addressed CVE-2023-40581 attempted to prevent RCE when using `--exec` with `%q` by replacing double quotes with two double quotes. However, this escaping is not sufficient, and still allows expansion of environment variables. 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 2024.04.09 fixes this issue by properly escaping `%`. It replaces them with `%%cd:~,%`, a variable that expands to nothing, leaving only the leading percent. It is recommended to upgrade yt-dlp to version 2024.04.09 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 `&`; and/or instead of using `--exec`, write the info json and load the fields from it instead.
Severity: nan (CVSS v3 base score: )
Weakness: NVD-CWE-noinfo \u2014 Insufficient Information
There is insufficient information about the issue to classify it; details are unkown or unspecified.
Repository: https://github.com/yt-dlp/yt-dlp
Files changed:
devscripts/changelog_override.json
test/test_utils.py
yt_dlp/YoutubeDL.py
yt_dlp/compat/__init__.py
yt_dlp/utils/_utils.py
Commit message: [core] Prevent RCE when using `--exec` with `%q` (CVE-2024-22423)

The shell escape function now properly escapes `%`, `\\` and `\n`. `utils.Popen` as well as `%q` output template expansion have been patched accordingly.

Prior to this fix using `--exec` together with `%q` when on Windows could cause remote code to execute. See https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-hjq6-52gw-2g7p for more details.

Authored by: Grub4K


Vulnerable code:
from .compat import compat_os_name, compat_shlex_quote, urllib_req_to_req
    args_to_str,
                args_to_str(correct_argv))
                value, fmt = ' '.join(map(compat_shlex_quote, value)), str_fmt
if compat_os_name == 'nt':
    def compat_shlex_quote(s):
        import re
        return s if re.match(r'^[-_\w./]+$', s) else s.replace('"', '""').join('""')
else:
    from shlex import quote as compat_shlex_quote  # noqa: F401
    compat_shlex_quote,
                args = ' '.join(compat_shlex_quote(a) for a in args)
            args = f'{self.__comspec()} /Q /S /D /V:OFF /C "{args}"'
def shell_quote(args):
    quoted_args = []
    encoding = get_filesystem_encoding()
    for a in args:
        if isinstance(a, bytes):
            # We may get a filename encoded with 'encodeFilename'
            a = a.decode(encoding)
        quoted_args.append(compat_shlex_quote(a))
    return ' '.join(quoted_args)
    return ' '.join(compat_shlex_quote(a) for a in args)

Fixed code:
    },
    {
        "action": "add",
        "when": "9590cc6b4768e190183d7d071a6c78170889116a",
        "short": "[priority] Security: [[CVE-2024-22423](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-22423)] [Prevent RCE when using `--exec` with `%q` on Windows](https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-hjq6-52gw-2g7p)\n    - The shell escape function now properly escapes `%`, `\\` and `\\n`.\n    - `utils.Popen` has been patched accordingly."
        assert run_shell(['echo', '%CMDCMDLINE:~-1%&']) == '"%CMDCMDLINE:~-1%&"\n'
        assert run_shell(['echo', 'a\nb']) == '"a"\n"b"\n'
        assert run_shell(['echo', '"']) == '""""\n'
        assert run_shell(['echo', '\\']) == '\\\n'
from .compat import compat_os_name, urllib_req_to_req
    shell_quote,
                shell_quote(correct_argv))
                value, fmt = shell_quote(value, shell=True), str_fmt
def compat_shlex_quote(s):
    from ..utils import shell_quote
    return shell_quote(s)
                args = shell_quote(args, shell=True)
            # Set variable for `cmd.exe` newline escaping (see `utils.shell_quote`)
            env['='] = '"^\n\n"'
            args = f'{self.__comspec()} /Q /S /D /V:OFF /E:ON /C "{args}"'
_WINDOWS_QUOTE_TRANS = str.maketrans({'"': '\\"', '\\': '\\\\'})
_CMD_QUOTE_TRANS = str.maketrans({
    # Keep quotes balanced by replacing them with `""` instead of `\\"`
    '"': '""',
    # Requires a variable `=` containing `"^\n\n"` (set in `utils.Popen`)
    # `=` should be unique since variables containing `=` cannot be set using cmd
    '\n': '%=%',
    # While we are only required to escape backslashes immediately before quotes,
    # we instead escape all of 'em anyways to be consistent
    '\\': '\\\\',
    # Use zero length variable replacement so `%` doesn't get expanded
    # `cd` is always set as long as extensions are enabled (`/E:ON` in `utils.Popen`)
    '%': '%%cd:~,%',
})


def shell_quote(args, *, shell=False):
    args = list(variadic(args))
    if any(isinstance(item, bytes) for item in args):
        deprecation_warning('Passing bytes to utils.shell_quote is deprecated')
        encoding = get_filesystem_encoding()
        for index, item in enumerate(args):
            if isinstance(item, bytes):
                args[index] = item.decode(encoding)

    if compat_os_name != 'nt':
        return shlex.join(args)

    trans = _CMD_QUOTE_TRANS if shell else _WINDOWS_QUOTE_TRANS
    return ' '.join(
        s if re.fullmatch(r'[\w#$*\-+./:?@\\]+', s, re.ASCII) else s.translate(trans).join('""')
        for s in args)
    return shell_quote(args)