GHSA-42H4-V29R-42QG

Vulnerability from github – Published: 2023-09-25 17:33 – Updated: 2023-09-26 13:57
VLAI?
Summary
yt-dlp on Windows vulnerable to `--exec` command injection when using `%q`
Details

Impact

yt-dlp allows the user to provide shell commands to be executed at various stages in its download process through the --exec flag. This flag allows output template expansion in its argument, so that video metadata values may be used in the shell commands. The metadata fields can be combined with the %q conversion, which is intended to quote/escape these values so they can be safely passed to the shell.

However, the escaping used for cmd (the shell used by Python's subprocess on Windows) did not properly escape special characters, which can allow for remote code execution if --exec is used directly with maliciously crafted remote data. This vulnerability only impacts yt-dlp on Windows, and the vulnerability is present regardless of whether yt-dlp is run from cmd or from PowerShell.

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/Jo66yyCpHcQ --exec "echo %(title)q"
[youtube] Extracting URL: https://youtu.be/Jo66yyCpHcQ
[youtube] Jo66yyCpHcQ: Downloading webpage
[youtube] Jo66yyCpHcQ: Downloading ios player API JSON
[youtube] Jo66yyCpHcQ: Downloading android player API JSON
[youtube] Jo66yyCpHcQ: Downloading m3u8 information
[info] Jo66yyCpHcQ: Downloading 1 format(s): 135+251
[download] Destination: ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f135.mp4
[download] 100% of    4.85KiB in 00:00:00 at 60.20KiB/s
[download] Destination: ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f251.webm
[download] 100% of    4.80KiB in 00:00:00 at 31.58KiB/s
[Merger] Merging formats into "＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].mkv"
Deleting original file ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f135.mp4 (pass -k to keep)
Deleting original file ＂&echo(&echo(pwned&rem( [Jo66yyCpHcQ].f251.webm (pass -k to keep)
[Exec] Executing command: echo "\"&echo(&echo(pwned&rem("
"\"

pwned

Patches

yt-dlp version 2023.09.24 fixes this issue by properly escaping each special character. \n will be replaced by \r, as no way of escaping it has been found.

Workarounds

It is recommended to upgrade yt-dlp to version 2023.09.24 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.

References

  • https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg
  • https://nvd.nist.gov/vuln/detail/CVE-2023-40581
  • https://github.com/yt-dlp/yt-dlp/releases/tag/2023.09.24
  • https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.09.24.003044
  • https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e
Severity ?
8.3 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "yt-dlp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2021.04.11"
            },
            {
              "fixed": "2023.09.24"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2023-40581"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-78"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-09-25T17:33:40Z",
    "nvd_published_at": "2023-09-25T19:15:09Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n[`yt-dlp`](https://github.com/yt-dlp/yt-dlp) allows the user to provide shell commands to be executed at various stages in its download process through the `--exec` flag. This flag allows output template expansion in its argument, so that video metadata values may be used in the shell commands. The metadata fields can be combined with the `%q` conversion, which is intended to quote/escape these values so they can be safely passed to the shell.\n\nHowever, the escaping used for `cmd` (the shell used by Python\u0027s `subprocess` on Windows) did not properly escape special characters, which can allow for remote code execution if `--exec` is used directly with maliciously crafted remote data. This vulnerability only impacts `yt-dlp` on Windows, and the vulnerability is present regardless of whether `yt-dlp` is run from `cmd` or from `PowerShell`.\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```shell\n\u003e yt-dlp https://youtu.be/Jo66yyCpHcQ --exec \"echo %(title)q\"\n[youtube] Extracting URL: https://youtu.be/Jo66yyCpHcQ\n[youtube] Jo66yyCpHcQ: Downloading webpage\n[youtube] Jo66yyCpHcQ: Downloading ios player API JSON\n[youtube] Jo66yyCpHcQ: Downloading android player API JSON\n[youtube] Jo66yyCpHcQ: Downloading m3u8 information\n[info] Jo66yyCpHcQ: Downloading 1 format(s): 135+251\n[download] Destination: \uff02\u0026echo(\u0026echo(pwned\u0026rem( [Jo66yyCpHcQ].f135.mp4\n[download] 100% of    4.85KiB in 00:00:00 at 60.20KiB/s\n[download] Destination: \uff02\u0026echo(\u0026echo(pwned\u0026rem( [Jo66yyCpHcQ].f251.webm\n[download] 100% of    4.80KiB in 00:00:00 at 31.58KiB/s\n[Merger] Merging formats into \"\uff02\u0026echo(\u0026echo(pwned\u0026rem( [Jo66yyCpHcQ].mkv\"\nDeleting original file \uff02\u0026echo(\u0026echo(pwned\u0026rem( [Jo66yyCpHcQ].f135.mp4 (pass -k to keep)\nDeleting original file \uff02\u0026echo(\u0026echo(pwned\u0026rem( [Jo66yyCpHcQ].f251.webm (pass -k to keep)\n[Exec] Executing command: echo \"\\\"\u0026echo(\u0026echo(pwned\u0026rem(\"\n\"\\\"\n\npwned\n```\n\n### Patches\nyt-dlp version 2023.09.24 fixes this issue by properly escaping each special character.\n`\\n` will be replaced by `\\r`, as no way of escaping it has been found.\n\n### Workarounds\nIt is recommended to upgrade yt-dlp to version 2023.09.24 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### References\n- https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg\n- https://nvd.nist.gov/vuln/detail/CVE-2023-40581\n- https://github.com/yt-dlp/yt-dlp/releases/tag/2023.09.24\n- https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.09.24.003044\n- https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e",
  "id": "GHSA-42h4-v29r-42qg",
  "modified": "2023-09-26T13:57:26Z",
  "published": "2023-09-25T17:33:40Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/security/advisories/GHSA-42h4-v29r-42qg"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-40581"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp/commit/de015e930747165dbb8fcd360f8775fd973b7d6e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/yt-dlp/yt-dlp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yt-dlp/yt-dlp-nightly-builds/releases/tag/2023.09.24.003044"
    },
    {
      "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/2023.09.24"
    }
  ],
  "schema_version": "1.4.0",
  "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 on Windows vulnerable to `--exec` command injection when using `%q`"
}


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