CVE-2024-22423 (published 2024-04-09T18:15Z)

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.


Weakness information:
cwe_id: NVD-CWE-noinfo
cwe_name: Insufficient Information
description: There is insufficient information about the issue to classify it; details are unkown or unspecified.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/yt-dlp/yt-dlp
commit_details: repo_url: https://github.com/yt-dlp/yt-dlp
author: Simon Sawicki
author_date: 2023-09-24 02:29:01+02:00
msg: [core] Prevent RCE when using `--exec` with `%q` (CVE-2023-40581)

The shell escape function is now using `""` instead of `\"`. `utils.Popen` has been patched to properly quote commands.

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-42h4-v29r-42qg for reference.

Authored by: Grub4K
repository: repo_url: https://github.com/yt-dlp/yt-dlp
repo_name: yt-dlp/yt-dlp
description: A feature-rich command-line audio/video downloader
repo_language: Python
owner: yt-dlp
file_changes: filename: changelog_override.json
change_type: ModificationType.MODIFY
diff: @@ -93,5 +93,10 @@
         "action": "add",
         "when": "c1d71d0d9f41db5e4306c86af232f5f6220a130b",
         "short": "[priority] **The minimum *recommended* Python version has been raised to 3.8**\nSince Python 3.7 has reached end-of-life, support for it will be dropped soon. [Read more](https://github.com/yt-dlp/yt-dlp/issues/7803)"
+    },
+    {
+        "action": "add",
+        "when": "61bdf15fc7400601c3da1aa7a43917310a5bf391",
+        "short": "[priority] Security: [[CVE-2023-40581](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40581)] [Prevent RCE when using `--exec` with `%q` on Windows](https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg)\n    - The shell escape function is now using `\"\"` instead of `\\\"`.\n    - `utils.Popen` has been patched to properly quote commands."
     }
 ]

programming_language: Jupyter Notebook
filename: test_YoutubeDL.py
change_type: ModificationType.MODIFY
diff: @@ -784,9 +784,9 @@ def expect_same_infodict(out):
         test('%(title4)#S', 'foo_bar_test')
         test('%(title4).10S', ('foo ＂bar＂ ', 'foo ＂bar＂' + ('#' if compat_os_name == 'nt' else ' ')))
         if compat_os_name == 'nt':
-            test('%(title4)q', ('"foo \\"bar\\" test"', "＂foo ⧹＂bar⧹＂ test＂"))
-            test('%(formats.:.id)#q', ('"id 1" "id 2" "id 3"', '＂id 1＂ ＂id 2＂ ＂id 3＂'))
-            test('%(formats.0.id)#q', ('"id 1"', '＂id 1＂'))
+            test('%(title4)q', ('"foo ""bar"" test"', None))
+            test('%(formats.:.id)#q', ('"id 1" "id 2" "id 3"', None))
+            test('%(formats.0.id)#q', ('"id 1"', None))
         else:
             test('%(title4)q', ('\'foo "bar" test\'', '\'foo ＂bar＂ test\''))
             test('%(formats.:.id)#q', "'id 1' 'id 2' 'id 3'")

programming_language: Python
filename: test_utils.py
change_type: ModificationType.MODIFY
diff: @@ -14,6 +14,7 @@
 import io
 import itertools
 import json
+import subprocess
 import xml.etree.ElementTree
 
 from yt_dlp.compat import (
@@ -28,6 +29,7 @@
     InAdvancePagedList,
     LazyList,
     OnDemandPagedList,
+    Popen,
     age_restricted,
     args_to_str,
     base_url,
@@ -2388,6 +2390,20 @@ def test_extract_basic_auth(self):
         assert extract_basic_auth('http://user:@foo.bar') == ('http://foo.bar', 'Basic dXNlcjo=')
         assert extract_basic_auth('http://user:pass@foo.bar') == ('http://foo.bar', 'Basic dXNlcjpwYXNz')
 
+    @unittest.skipUnless(compat_os_name == 'nt', 'Only relevant on Windows')
+    def test_Popen_windows_escaping(self):
+        def run_shell(args):
+            stdout, stderr, error = Popen.run(
+                args, text=True, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+            assert not stderr
+            assert not error
+            return stdout
+
+        # Test escaping
+        assert run_shell(['echo', 'test"&']) == '"test""&"\n'
+        # Test if delayed expansion is disabled
+        assert run_shell(['echo', '^!']) == '"^!"\n'
+        assert run_shell('echo "^!"') == '"^!"\n'
 
 if __name__ == '__main__':
     unittest.main()

programming_language: Python
filename: __init__.py
change_type: ModificationType.MODIFY
diff: @@ -30,7 +30,7 @@ def compat_etree_fromstring(text):
 if compat_os_name == 'nt':
     def compat_shlex_quote(s):
         import re
-        return s if re.match(r'^[-_\w./]+$', s) else '"%s"' % s.replace('"', '\\"')
+        return s if re.match(r'^[-_\w./]+$', s) else s.replace('"', '""').join('""')
 else:
     from shlex import quote as compat_shlex_quote  # noqa: F401
 

programming_language: Python
filename: exec.py
change_type: ModificationType.MODIFY
diff: @@ -1,8 +1,6 @@
-import subprocess
-
 from .common import PostProcessor
 from ..compat import compat_shlex_quote
-from ..utils import PostProcessingError, encodeArgument, variadic
+from ..utils import Popen, PostProcessingError, variadic
 
 
 class ExecPP(PostProcessor):
@@ -27,10 +25,10 @@ def parse_cmd(self, cmd, info):
     def run(self, info):
         for tmpl in self.exec_cmd:
             cmd = self.parse_cmd(tmpl, info)
-            self.to_screen('Executing command: %s' % cmd)
-            retCode = subprocess.call(encodeArgument(cmd), shell=True)
-            if retCode != 0:
-                raise PostProcessingError('Command returned error code %d' % retCode)
+            self.to_screen(f'Executing command: {cmd}')
+            _, _, return_code = Popen.run(cmd, shell=True)
+            if return_code != 0:
+                raise PostProcessingError(f'Command returned error code {return_code}')
         return [], info
 
 

programming_language: Python
filename: _utils.py
change_type: ModificationType.MODIFY
diff: @@ -825,7 +825,7 @@ def _fix(key):
         _fix('LD_LIBRARY_PATH')  # Linux
         _fix('DYLD_LIBRARY_PATH')  # macOS
 
-    def __init__(self, *args, env=None, text=False, **kwargs):
+    def __init__(self, args, *remaining, env=None, text=False, shell=False, **kwargs):
         if env is None:
             env = os.environ.copy()
         self._fix_pyinstaller_ld_path(env)
@@ -835,7 +835,21 @@ def __init__(self, *args, env=None, text=False, **kwargs):
             kwargs['universal_newlines'] = True  # For 3.6 compatibility
             kwargs.setdefault('encoding', 'utf-8')
             kwargs.setdefault('errors', 'replace')
-        super().__init__(*args, env=env, **kwargs, startupinfo=self._startupinfo)
+
+        if shell and compat_os_name == 'nt' and kwargs.get('executable') is None:
+            if not isinstance(args, str):
+                args = ' '.join(compat_shlex_quote(a) for a in args)
+            shell = False
+            args = f'{self.__comspec()} /Q /S /D /V:OFF /C "{args}"'
+
+        super().__init__(args, *remaining, env=env, shell=shell, **kwargs, startupinfo=self._startupinfo)
+
+    def __comspec(self):
+        comspec = os.environ.get('ComSpec') or os.path.join(
+            os.environ.get('SystemRoot', ''), 'System32', 'cmd.exe')
+        if os.path.isabs(comspec):
+            return comspec
+        raise FileNotFoundError('shell not found: neither %ComSpec% nor %SystemRoot% is set')
 
     def communicate_or_kill(self, *args, **kwargs):
         try:

programming_language: Python
repo_url: https://github.com/yt-dlp/yt-dlp
commit_details: repo_url: https://github.com/yt-dlp/yt-dlp
author: Simon Sawicki
author_date: 2024-04-08 23:18:04+02:00
msg: [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
repository: repo_url: https://github.com/yt-dlp/yt-dlp
repo_name: yt-dlp/yt-dlp
description: A feature-rich command-line audio/video downloader
repo_language: Python
owner: yt-dlp
file_changes: filename: changelog_override.json
change_type: ModificationType.MODIFY
diff: @@ -142,5 +142,10 @@
         "when": "e3a3ed8a981d9395c4859b6ef56cd02bc3148db2",
         "short": "[cleanup:ie] No `from` stdlib imports in extractors",
         "authors": ["pukkandan"]
+    },
+    {
+        "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."
     }
 ]

programming_language: Jupyter Notebook
filename: test_utils.py
change_type: ModificationType.MODIFY
diff: @@ -2069,6 +2069,10 @@ def run_shell(args):
 
         # Test escaping
         assert run_shell(['echo', 'test"&']) == '"test""&"\n'
+        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'
         # Test if delayed expansion is disabled
         assert run_shell(['echo', '^!']) == '"^!"\n'
         assert run_shell('echo "^!"') == '"^!"\n'

programming_language: Python
filename: YoutubeDL.py
change_type: ModificationType.MODIFY
diff: @@ -25,7 +25,7 @@
 
 from .cache import Cache
 from .compat import functools, urllib  # isort: split
-from .compat import compat_os_name, compat_shlex_quote, urllib_req_to_req
+from .compat import compat_os_name, urllib_req_to_req
 from .cookies import LenientSimpleCookie, load_cookies
 from .downloader import FFmpegFD, get_suitable_downloader, shorten_protocol_name
 from .downloader.rtmp import rtmpdump_version
@@ -102,7 +102,6 @@
     UserNotLive,
     YoutubeDLError,
     age_restricted,
-    args_to_str,
     bug_reports_message,
     date_from_str,
     deprecation_warning,
@@ -141,6 +140,7 @@
     sanitize_filename,
     sanitize_path,
     sanitize_url,
+    shell_quote,
     str_or_none,
     strftime_or_none,
     subtitles_filename,
@@ -823,7 +823,7 @@ def warn_if_short_id(self, argv):
             self.report_warning(
                 'Long argument string detected. '
                 'Use -- to separate parameters and URLs, like this:\n%s' %
-                args_to_str(correct_argv))
+                shell_quote(correct_argv))
 
     def add_info_extractor(self, ie):
         """Add an InfoExtractor object to the end of the list."""
@@ -1355,7 +1355,7 @@ def create_key(outer_mobj):
                 value, fmt = escapeHTML(str(value)), str_fmt
             elif fmt[-1] == 'q':  # quoted
                 value = map(str, variadic(value) if '#' in flags else [value])
-                value, fmt = ' '.join(map(compat_shlex_quote, value)), str_fmt
+                value, fmt = shell_quote(value, shell=True), str_fmt
             elif fmt[-1] == 'B':  # bytes
                 value = f'%{str_fmt}'.encode() % str(value).encode()
                 value, fmt = value.decode('utf-8', 'ignore'), 's'

programming_language: Python
filename: __init__.py
change_type: ModificationType.MODIFY
diff: @@ -27,12 +27,9 @@ def compat_etree_fromstring(text):
 compat_os_name = os._name if os.name == 'java' else os.name
 
 
-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
+def compat_shlex_quote(s):
+    from ..utils import shell_quote
+    return shell_quote(s)
 
 
 def compat_ord(c):

programming_language: Python
filename: _utils.py
change_type: ModificationType.MODIFY
diff: @@ -50,7 +50,6 @@
     compat_expanduser,
     compat_HTMLParseError,
     compat_os_name,
-    compat_shlex_quote,
 )
 from ..dependencies import xattr
 
@@ -836,9 +835,11 @@ def __init__(self, args, *remaining, env=None, text=False, shell=False, **kwargs
 
         if shell and compat_os_name == 'nt' and kwargs.get('executable') is None:
             if not isinstance(args, str):
-                args = ' '.join(compat_shlex_quote(a) for a in args)
+                args = shell_quote(args, shell=True)
             shell = False
-            args = f'{self.__comspec()} /Q /S /D /V:OFF /C "{args}"'
+            # 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}"'
 
         super().__init__(args, *remaining, env=env, shell=shell, **kwargs, startupinfo=self._startupinfo)
 
@@ -1637,15 +1638,38 @@ def get_filesystem_encoding():
     return encoding if encoding is not None else 'utf-8'
 
 
-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)
+_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)
 
 
 def smuggle_url(url, data):
@@ -2849,7 +2873,7 @@ def ytdl_is_updateable():
 
 def args_to_str(args):
     # Get a short string representation for a subprocess command
-    return ' '.join(compat_shlex_quote(a) for a in args)
+    return shell_quote(args)
 
 
 def error_to_str(err):

programming_language: Python