PYSEC-2026-2066

Vulnerability from pysec - Published: 2026-07-07 11:45 - Updated: 2026-07-07 17:25
VLAI
Details

Summary

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 "https://youtu.be/42xO6rVqf2E" --ignore-config -f 18 --exec "echo %(title)q"
[youtube] Extracting URL: https://youtu.be/42xO6rVqf2E
[youtube] 42xO6rVqf2E: Downloading webpage
[youtube] 42xO6rVqf2E: Downloading ios player API JSON
[youtube] 42xO6rVqf2E: Downloading android player API JSON
[youtube] 42xO6rVqf2E: Downloading m3u8 information
[info] 42xO6rVqf2E: Downloading 1 format(s): 18
[download] Destination: %CMDCMDLINE：~-1%&echo pwned&calc.exe [42xO6rVqf2E].mp4
[download] 100% of  126.16KiB in 00:00:00 at 2.46MiB/s
[Exec] Executing command: echo "%CMDCMDLINE:~-1%&echo pwned&calc.exe"
""
pwned

Patches

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.

Workarounds

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 &. - Instead of using --exec, write the info json and load the fields from it instead.

Details

When escaping variables, the following code is used for Windows. yt_dlp/compat/__init__.py line 31-33

    def compat_shlex_quote(s):
        import re
        return s if re.match(r'^[-_\w./]+$', s) else s.replace('"', '""').join('""')

It replaces " with "" to balance out the quotes and keep quoting intact if non-allowed characters are included. However, the %CMDCMDLINE% variable can be used to generate a quote using %CMDCMDLINE:~-1%; since the value of %CMDCMDLINE% is the commandline with which cmd.exe was called, and it is always called with the command surrounded by quotes, %CMDCMDLINE:~-1% expands to ". After the quotes have been unbalanced, special characters are no longer quoted and commands can be executed:

%CMDCMDLINE:~-1%&calc.exe

References

  • https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-hjq6-52gw-2g7p
  • https://nvd.nist.gov/vuln/detail/CVE-2024-22423
  • https://github.com/yt-dlp/yt-dlp/releases/tag/2024.04.09
  • https://github.com/yt-dlp/yt-dlp/commit/ff07792676f404ffff6ee61b5638c9dc1a33a37a
Severity
8.3 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
Impacted products
Name purl
yt-dlp pkg:pypi/yt-dlp
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "yt-dlp",
        "purl": "pkg:pypi/yt-dlp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2021.04.11"
            },
            {
              "fixed": "2024.04.09"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2021.10.10",
        "2021.10.22",
        "2021.10.9",
        "2021.11.10",
        "2021.11.10.1",
        "2021.12.1",
        "2021.12.25",
        "2021.12.27",
        "2021.4.11",
        "2021.4.22",
        "2021.5.11",
        "2021.5.20",
        "2021.6.1",
        "2021.6.23",
        "2021.6.8",
        "2021.6.9",
        "2021.7.21",
        "2021.7.24",
        "2021.7.7",
        "2021.8.10",
        "2021.8.2",
        "2021.9.1",
        "2021.9.2",
        "2021.9.25",
        "2022.1.21",
        "2022.10.4",
        "2022.11.11",
        "2022.2.3",
        "2022.2.4",
        "2022.3.8",
        "2022.3.8.1",
        "2022.3.8.2",
        "2022.4.8",
        "2022.5.18",
        "2022.6.22",
        "2022.6.22.1",
        "2022.6.29",
        "2022.7.17",
        "2022.7.18",
        "2022.8.14",
        "2022.8.19",
        "2022.8.8",
        "2022.9.1",
        "2023.1.2",
        "2023.1.6",
        "2023.10.13",
        "2023.10.7",
        "2023.11.13.232715.dev0",
        "2023.11.13.5826.dev0",
        "2023.11.14",
        "2023.11.15.232826.dev0",
        "2023.11.16",
        "2023.11.16.232727.dev0",
        "2023.11.18.232705.dev0",
        "2023.11.19.232719.dev0",
        "2023.11.20.232729.dev0",
        "2023.11.26.232703.dev0",
        "2023.11.28.232715.dev0",
        "2023.11.29.232714.dev0",
        "2023.12.12.232727.dev0",
        "2023.12.13.232710.dev0",
        "2023.12.17.232710.dev0",
        "2023.12.18.232711.dev0",
        "2023.12.19.232701.dev0",
        "2023.12.20.232717.dev0",
        "2023.12.21.232720.dev0",
        "2023.12.22.232735.dev0",
        "2023.12.24.232657.dev0",
        "2023.12.26.232752.dev0",
        "2023.12.30",
        "2023.12.30.232719.dev0",
        "2023.12.31.232713.dev0",
        "2023.12.5.232702.dev0",
        "2023.12.6.232721.dev0",
        "2023.2.17",
        "2023.3.3",
        "2023.3.4",
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        "2023.6.22",
        "2023.7.6",
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        "2024.1.14.232710.dev0",
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        "2024.1.28.232706.dev0",
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        "2024.1.31.232703.dev0",
        "2024.1.5.232702.dev0",
        "2024.1.8.232709.dev0",
        "2024.1.9.232723.dev0",
        "2024.2.13.232701.dev0",
        "2024.2.14.232704.dev0",
        "2024.2.15.232705.dev0",
        "2024.2.16.232705.dev0",
        "2024.2.17.232706.dev0",
        "2024.2.18.232707.dev0",
        "2024.2.19.232703.dev0",
        "2024.2.2.232707.dev0",
        "2024.2.20.232712.dev0",
        "2024.2.21.232721.dev0",
        "2024.2.22.232849.dev0",
        "2024.2.23.232656.dev0",
        "2024.2.24.232815.dev0",
        "2024.2.25.232703.dev0",
        "2024.2.28.232744.dev0",
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        "2024.2.3.232712.dev0",
        "2024.2.4.232659.dev0",
        "2024.2.5.232712.dev0",
        "2024.2.9.232659.dev0",
        "2024.3.10",
        "2024.3.10.232703.dev0",
        "2024.3.14.232657.dev0",
        "2024.3.17.232657.dev0",
        "2024.3.18.232707.dev0",
        "2024.3.19.232701.dev0",
        "2024.3.2.232720.dev0",
        "2024.3.20.232704.dev0",
        "2024.3.22.232703.dev0",
        "2024.3.29.232706.dev0",
        "2024.3.3.232706.dev0",
        "2024.3.30.232704.dev0",
        "2024.3.31.232706.dev0",
        "2024.3.4.232716.dev0",
        "2024.3.6.232659.dev0",
        "2024.3.7.232716.dev0",
        "2024.3.8.232718.dev0",
        "2024.3.9.232714.dev0",
        "2024.4.1.232704.dev0",
        "2024.4.3.233315.dev0",
        "2024.4.4.232729.dev0",
        "2024.4.6.232655.dev0",
        "2024.4.7.232657.dev0",
        "2024.4.8.232708.dev0"
      ]
    }
  ],
  "aliases": [
    "CVE-2024-22423",
    "GHSA-hjq6-52gw-2g7p"
  ],
  "details": "### Summary\nThe [patch that addressed CVE-2023-40581](https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e) attempted to prevent RCE when using `--exec` with `%q` by replacing double quotes with two double quotes.\nHowever, this escaping is not sufficient, and still allows expansion of environment variables.\n\nSupport for output template expansion in `--exec`, along with this vulnerable behavior, was added to `yt-dlp` in version [2021.04.11](https://github.com/yt-dlp/yt-dlp/releases/tag/2021.04.11).\n\n```cmd\n\u003e yt-dlp \"https://youtu.be/42xO6rVqf2E\" --ignore-config -f 18 --exec \"echo %(title)q\"\n[youtube] Extracting URL: https://youtu.be/42xO6rVqf2E\n[youtube] 42xO6rVqf2E: Downloading webpage\n[youtube] 42xO6rVqf2E: Downloading ios player API JSON\n[youtube] 42xO6rVqf2E: Downloading android player API JSON\n[youtube] 42xO6rVqf2E: Downloading m3u8 information\n[info] 42xO6rVqf2E: Downloading 1 format(s): 18\n[download] Destination: %CMDCMDLINE\uff1a~-1%\u0026echo pwned\u0026calc.exe [42xO6rVqf2E].mp4\n[download] 100% of  126.16KiB in 00:00:00 at 2.46MiB/s\n[Exec] Executing command: echo \"%CMDCMDLINE:~-1%\u0026echo pwned\u0026calc.exe\"\n\"\"\npwned\n```\n\n### Patches\nyt-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.\n\n### Workarounds\nIt 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.\n\nFor Windows users who are not able to upgrade:\n- Avoid using any output template expansion in `--exec` other than `{}` (filepath).\n- If expansion in `--exec` is needed, verify the fields you are using do not contain `%`, `\"`, `|` or `\u0026`.\n- Instead of using `--exec`, write the info json and load the fields from it instead.\n\n### Details\nWhen escaping variables, the following code is used for Windows.\n[`yt_dlp/compat/__init__.py` line 31-33](https://github.com/yt-dlp/yt-dlp/blob/8e6e3651727b0b85764857fc6329fe5e0a3f00de/yt_dlp/compat/__init__.py#L31-L33)\n```python\n    def compat_shlex_quote(s):\n        import re\n        return s if re.match(r\u0027^[-_\\w./]+$\u0027, s) else s.replace(\u0027\"\u0027, \u0027\"\"\u0027).join(\u0027\"\"\u0027)\n```\nIt replaces `\"` with `\"\"` to balance out the quotes and keep quoting intact if non-allowed characters are included. However, the `%CMDCMDLINE%` variable can be used to generate a quote using `%CMDCMDLINE:~-1%`; since the value of `%CMDCMDLINE%` is the commandline with which `cmd.exe` was called, and it is always called with the command surrounded by quotes, `%CMDCMDLINE:~-1%` expands to `\"`. After the quotes have been unbalanced, special characters are no longer quoted and commands can be executed:\n```cmd\n%CMDCMDLINE:~-1%\u0026calc.exe\n```\n\n### References\n- https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-hjq6-52gw-2g7p\n- https://nvd.nist.gov/vuln/detail/CVE-2024-22423\n- https://github.com/yt-dlp/yt-dlp/releases/tag/2024.04.09\n- https://github.com/yt-dlp/yt-dlp/commit/ff07792676f404ffff6ee61b5638c9dc1a33a37a",
  "id": "PYSEC-2026-2066",
  "modified": "2026-07-07T17:25:52.844224Z",
  "published": "2026-07-07T11:45:37.839656Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-hjq6-52gw-2g7p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-22423"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/commit/ff07792676f404ffff6ee61b5638c9dc1a33a37a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/yt-dlp/yt-dlp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/releases/tag/2021.04.11"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/releases/tag/2024.04.09"
    },
    {
      "type": "WEB",
      "url": "https://www.kb.cert.org/vuls/id/123335"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/yt-dlp"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-hjq6-52gw-2g7p"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "yt-dlp: `--exec` command injection when using `%q` in yt-dlp on Windows (Bypass of CVE-2023-40581)"
}



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